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Chen W, Caston R, Balakrishnan B, Siddiqi A, Parmar K, Tang M, Feng M, Lai K. Assessment of ataxia phenotype in a new mouse model of galactose-1 phosphate uridylyltransferase (GALT) deficiency. J Inherit Metab Dis 2017; 40:131-137. [PMID: 27783170 PMCID: PMC5203948 DOI: 10.1007/s10545-016-9993-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Revised: 10/10/2016] [Accepted: 10/11/2016] [Indexed: 12/14/2022]
Abstract
Despite adequate dietary management, patients with classic galactosemia continue to have increased risks of cognitive deficits, speech dyspraxia, primary ovarian insufficiency, and abnormal motor development. A recent evaluation of a new galactose-1 phosphate uridylyltransferase (GALT)-deficient mouse model revealed reduced fertility and growth restriction. These phenotypes resemble those seen in human patients. In this study, we further assess the fidelity of this new mouse model by examining the animals for the manifestation of a common neurological sequela in human patients: cerebellar ataxia. The balance, grip strength, and motor coordination of GALT-deficient and wild-type mice were tested using a modified rotarod. The results were compared to composite phenotype scoring tests, typically used to evaluate neurological and motor impairment. The data demonstrated abnormalities with varying severity in the GALT-deficient mice. Mice of different ages were used to reveal the progressive nature of motor impairment. The varying severity and age-dependent impairments seen in the animal model agree with reports on human patients. Finally, measurements of the cerebellar granular and molecular layers suggested that mutant mice experience cerebellar hypoplasia, which could have resulted from the down-regulation of the PI3K/Akt signaling pathway.
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Affiliation(s)
- Wyman Chen
- Department of Pediatrics, University of Utah School of Medicine, 295 Chipeta Way, Salt Lake City, UT, 84108, USA
| | - Rose Caston
- Department of Pediatrics, University of Utah School of Medicine, 295 Chipeta Way, Salt Lake City, UT, 84108, USA
- Dartmouth College, Hanover, NH, USA
| | - Bijina Balakrishnan
- Department of Pediatrics, University of Utah School of Medicine, 295 Chipeta Way, Salt Lake City, UT, 84108, USA
| | - Anwer Siddiqi
- Department of Pathology and Laboratory Medicine, University of Florida College of Medicine, Jacksonville, FL, USA
| | - Kamalpreet Parmar
- Department of Pathology and Laboratory Medicine, University of Florida College of Medicine, Jacksonville, FL, USA
| | - Manshu Tang
- Department of Pediatrics, University of Utah School of Medicine, 295 Chipeta Way, Salt Lake City, UT, 84108, USA
| | - Merry Feng
- Department of Pediatrics, University of Utah School of Medicine, 295 Chipeta Way, Salt Lake City, UT, 84108, USA
| | - Kent Lai
- Department of Pediatrics, University of Utah School of Medicine, 295 Chipeta Way, Salt Lake City, UT, 84108, USA.
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Brokate-Llanos AM, Monje JM, Murdoch PDS, Muñoz MJ. Developmental defects in a Caenorhabditis elegans model for type III galactosemia. Genetics 2014; 198:1559-69. [PMID: 25298520 PMCID: PMC4256771 DOI: 10.1534/genetics.114.170084] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 10/01/2014] [Indexed: 12/21/2022] Open
Abstract
Type III galactosemia is a metabolic disorder caused by reduced activity of UDP-galactose-4-epimerase, which participates in galactose metabolism and the generation of various UDP-sugar species. We characterized gale-1 in Caenorhabditis elegans and found that a complete loss-of-function mutation is lethal, as has been hypothesized for humans, whereas a nonlethal partial loss-of-function allele causes a variety of developmental abnormalities, likely resulting from the impairment of the glycosylation process. We also observed that gale-1 mutants are hypersensitive to galactose as well as to infections. Interestingly, we found interactions between gale-1 and the unfolded protein response.
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Affiliation(s)
- Ana M Brokate-Llanos
- Centro Andaluz de Biología del Desarrollo, Consejo Superior de Investigaciones Científicas-Universidad Pablo de Olavide-Junta de Andalucía, 41013 Seville, Spain
| | - José M Monje
- Centro Andaluz de Biología del Desarrollo, Consejo Superior de Investigaciones Científicas-Universidad Pablo de Olavide-Junta de Andalucía, 41013 Seville, Spain
| | - Piedad Del Socorro Murdoch
- Departamento de Bioquímica y Biología Molecular, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
| | - Manuel J Muñoz
- Centro Andaluz de Biología del Desarrollo, Consejo Superior de Investigaciones Científicas-Universidad Pablo de Olavide-Junta de Andalucía, 41013 Seville, Spain
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McCorvie TJ, Gleason TJ, Fridovich-Keil JL, Timson DJ. Misfolding of galactose 1-phosphate uridylyltransferase can result in type I galactosemia. Biochim Biophys Acta Mol Basis Dis 2013; 1832:1279-93. [PMID: 23583749 DOI: 10.1016/j.bbadis.2013.04.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 03/27/2013] [Accepted: 04/02/2013] [Indexed: 11/17/2022]
Abstract
Type I galactosemia is a genetic disorder that is caused by the impairment of galactose-1-phosphate uridylyltransferase (GALT; EC 2.7.7.12). Although a large number of mutations have been detected through genetic screening of the human GALT (hGALT) locus, for many it is not known how they cause their effects. The majority of these mutations are missense, with predicted substitutions scattered throughout the enzyme structure and thus causing impairment by other means rather than direct alterations to the active site. To clarify the fundamental, molecular basis of hGALT impairment we studied five disease-associated variants p.D28Y, p.L74P, p.F171S, p.F194L and p.R333G using both a yeast model and purified, recombinant proteins. In a yeast expression system there was a correlation between lysate activity and the ability to rescue growth in the presence of galactose, except for p.R333G. Kinetic analysis of the purified proteins quantified each variant's level of enzymatic impairment and demonstrated that this was largely due to altered substrate binding. Increased surface hydrophobicity, altered thermal stability and changes in proteolytic sensitivity were also detected. Our results demonstrate that hGALT requires a level of flexibility to function optimally and that altered folding is the underlying reason of impairment in all the variants tested here. This indicates that misfolding is a common, molecular basis of hGALT deficiency and suggests the potential of pharmacological chaperones and proteostasis regulators as novel therapeutic approaches for type I galactosemia.
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Affiliation(s)
- Thomas J McCorvie
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, BT9 7BL, UK
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Schmidt D, Shin YS, Auw-Haedrich C, Tacke U. Congenital ocular malformations (lens subluxation, pupillary displacement, cataract, myopia) and classic galactosaemia associated with Q188R and /or G1391A mutations. Acta Ophthalmol 2011; 89:489-94. [PMID: 20222886 DOI: 10.1111/j.1755-3768.2009.01691.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE Observations of multiple ocular malformations together with heterozygosity for galactosaemia in siblings and homozygosity in one child are highly unusual. In these case histories, a series of investigations in one family are reported. METHODS Members of a family of two brothers and one sister and their children were pre- and post-surgically examined over several years. Blood examination was carried out in a laboratory specializing in investigation into genetic diseases (Dr Podskarbi, Munich). RESULTS Two brothers and one sister suffered from cataract-induced visual deterioration at 38, 34 and 35 years of age, respectively. All three siblings reported having had bilateral poor vision since early childhood. The three siblings' parents had no congenital ocular malformations, nor was there any parental consanguinity. One child, the 10-year-old son of the 35-year-old sister, exhibited classic galactosaemia and normal ocular findings. This sister's other child was healthy. All three siblings presented congenital lens luxation, axial myopia, cataract and iridodonesis. In addition, the 34-year-old brother showed unilateral right corectopia and left coloboma adjacent to the optic disc. The 38-year-old brother revealed myopic fundus changes, but no coloboma. The three siblings experienced a distinct increase in visual acuity after cataract surgery. Both eyes of the patients were partially or distinctly amblyopic, respectively. We assume an autosomal-recessive transmission. Molecular genetic examination of the 10-year-old child with classic galactosaemia showed homozygosity for the mutation Q188R with a complete galactose-1-phosphate-uridyltransferase (GALT) deficiency. Because of his galactose-free diet, the child showed normal values for galactose-1-phosphate. The 35-year-old mother showed compound heterozygosity for Q188R and G1391A (D2/G). The 10-year-old boy's father also revealed heterozygosity for galactosaemia caused by GALT deficiency. The two children of the 38-year-old brother were heterozygous for G1391A. They did not show any clinical abnormality. None of the family members had clinical signs of Marfan's syndrome or homocysteinuria. The three siblings' parents were not consanguineous. CONCLUSIONS Patients with worsening cataracts occurring at a pre-senile age should be examined for galactosaemia. We describe for the first time the molecular genetic findings in congenital ectopia lentis et pupillae. Early treatment in conjunction with a galactose-free diet is mandatory in patients with galactosaemia. Members of a family with heterozygosity for galactosaemia should be advised to attend a human genetic consultation.
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Affiliation(s)
- Dieter Schmidt
- University of Freiburg Eye Clinic (Universitäts-Augenklinik), Freiburg, Germany.
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Camelo JS, Fernandes MIM, Maciel LMZ, Scrideli CA, Santos JLF, Camargo AS, Passador CS, Leite PC, Resende DR, de Souza LO, Giugliani R, Jorge SM. Galactosaemia in a Brazilian population: high incidence and cost-benefit analysis. J Inherit Metab Dis 2009; 32 Suppl 1:S141-9. [PMID: 19418240 DOI: 10.1007/s10545-009-1112-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Revised: 03/20/2009] [Accepted: 03/25/2009] [Indexed: 10/20/2022]
Abstract
OBJECTIVES To study the incidence of galactosaemia in the state of São Paulo and the benefit/cost (B/C) ratio of the introduction of neonatal screening for galactosaemia, comparing it with a selective approach. METHODS An enzymatic-colorimetric assay was used for the screening of total galactose (TG) in a sample of 10% of the births in São Paulo in one year and positive cases were confirmed by the activity of galactose-1-phosphate uridyltransferase (GALT). Detected and referred cases were genotyped using enzyme restriction studies for Q188R, N314D and S135L mutations of the GALT gene. The economic analysis was determined by calculating the B/C ratio and by analysis of sensitivity as a function of the incidence of the disease detected and the variation of the interest rate in the economy. RESULTS 59 953 newborns were screened for TG, with 3 cases of galactosaemia being identified (0.26% false positives), corresponding to a frequency of 1:19 984 liveborns (95% confidence interval: 1:7494 to 1:59 953). One classical case and one Duarte 2 variant referred to as a selective approach were confirmed. With an incidence of 1:19 984, the B/C ratio was 1.04 for the 11.75% interest rate in effect in Brazil, with values already decapitalized. With a maximum possible incidence of 1:7494, the B/C ratio was 2.79. DISCUSSION There is an economic advantage in introducing neonatal screening for galactosaemia in the national neonatal screening programme. This advantage could increase with a reduction of the current interest rates in the economy.
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Affiliation(s)
- J S Camelo
- Department of Pediatrics, School of Medicine of Ribeirão Preto, University of São Paulo, Bandeirantes Avenue, 3900, Clinics Hospital, Monte Alegre Campus, Ribeirão Preto, São Paulo, Brazil.
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Crushell E, Chukwu J, Mayne P, Blatny J, Treacy EP. Negative screening tests in classical galactosaemia caused by S135L homozygosity. J Inherit Metab Dis 2009; 32:412-5. [PMID: 19418241 DOI: 10.1007/s10545-009-1081-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Revised: 03/15/2009] [Accepted: 03/19/2009] [Indexed: 10/20/2022]
Abstract
Classical galactosaemia is relatively common in Ireland due to a high carrier rate of the Q188R GALT mutation. It is screened for using a bacterial inhibition assay (BIA) for free galactose. A Beutler assay on day one of life is performed only in high risk cases (infants of the Traveller community and relatives of known cases). A 16-month-old Irish-born boy of Nigerian origin was referred for investigation of developmental delay, and failure to thrive. He had oral aversion to solids and his diet consisted of cow's milk and milk-based cereal mixes. He was found to have microcephaly, weight <2nd percentile, hepatomegaly and bilateral cataracts. Coagulation screen was normal and transaminases were slightly elevated. His original newborn screen was reviewed and confirmed to have been negative; urinary reducing substances on three separate occasions were negative. Beutler assay demonstrated "absent" red cell galactose-1-phosphate uridyltransferase (GALT) activity. GALT enzyme activity was <0.5 gsubs/h per gHb confirming classical galactosaemia. Gal-1-P was elevated at 1.88 micromol/gHb. Mutation analysis of the GALT gene revealed S135L homozygosity. S135L/S135L galactosaemia is associated with absent red cell GALT activity but with approximately 10% activity in other tissues such as the liver and intestines, probably explaining the negative screening tests and the somewhat milder phenotype associated with this genotype. The patient was commenced on galactose-restricted diet; on follow-up at 2 years of age, growth had normalized but there was global developmental delay. In conclusion, galactosaemia must be considered in children who present with poor growth, hepatomegaly, developmental delay and cataracts and GALT enzyme analysis should be a first line test in such cases. Non-enzymatic screening methods such as urinary reducing substances and BIA for free galactose are not reliable in S135L homozygous galactosaemia.
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Affiliation(s)
- E Crushell
- National Centre for Inherited Metabolic Disorders, Children's University Hospital, Temple St, Dublin 1, Ireland.
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Chhay JS, Openo KK, Eaton JS, Gentile M, Fridovich-Keil JL. A yeast model reveals biochemical severity associated with each of three variant alleles of galactose-1P uridylyltransferase segregating in a single family. J Inherit Metab Dis 2008; 31:97-107. [PMID: 18210213 DOI: 10.1007/s10545-007-0786-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2007] [Revised: 11/20/2007] [Accepted: 12/04/2007] [Indexed: 10/22/2022]
Abstract
Classic galactosaemia is a potentially lethal inborn error of metabolism that results from profound impairment of galactose-1P uridylyltransferase (GALT). Like many autosomal recessive disorders, classic galactosaemia demonstrates marked allelic heterogeneity; many if not most patients are compound heterozygotes. Owing in part to the fact that most GALT mutations are never observed in patients in the homozygous state, in part to concerns of possible allelic interaction, and in part to the broad range of GALT activity levels associated with the affected, carrier, and control states, definition of the specific functional consequence of individual variant GALT alleles from studies of clinical samples alone can be a challenging task. To overcome this problem we previously developed and applied a null-background yeast system to enable functional analyses of human GALT alleles expressed individually or in defined pairs. We report here the application of this system to characterize three distinct variant alleles of GALT identified within a single family. Of these alleles, one carried a missense mutation (K285N) that has previously been reported and characterized, one carried a nonsense mutation (R204X) that has previously been reported but not characterized, and the third carried a missense substitution (T268N) that was novel. Our studies reported here reconfirm the profound nature of the K285N mutation, demonstrate that the R204X mutation severely compromises both expression and function of human GALT, and finally implicate T268N as one of a very small number of naturally occurring rare but neutral missense polymorphisms in human GALT.
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Affiliation(s)
- J S Chhay
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA
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Mumma JO, Chhay JS, Ross KL, Eaton JS, Newell-Litwa KA, Fridovich-Keil JL. Distinct roles of galactose-1P in galactose-mediated growth arrest of yeast deficient in galactose-1P uridylyltransferase (GALT) and UDP-galactose 4'-epimerase (GALE). Mol Genet Metab 2008; 93:160-71. [PMID: 17981065 PMCID: PMC2253667 DOI: 10.1016/j.ymgme.2007.09.012] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2007] [Revised: 09/24/2007] [Accepted: 09/24/2007] [Indexed: 10/22/2022]
Abstract
Galactose is metabolized in humans and other species by the three-enzyme Leloir pathway comprised of galactokinase (GALK), galactose 1-P uridylyltransferase (GALT), and UDP-galactose 4'-epimerase (GALE). Impairment of GALT or GALE in humans results in the potentially lethal disorder galactosemia, and loss of either enzyme in yeast results in galactose-dependent growth arrest of cultures despite the availability of an alternate carbon source. In contrast, loss of GALK in humans is not life-threatening, and in yeast has no impact on the growth of cultures challenged with galactose. Further, the growth of both GALT-null and GALE-null yeast challenged with galactose is rescued by loss of GALK, thereby implicating the GALK reaction product, gal-1P, for a role in the galactose-sensitivity of both strains. However, the nature of that relationship has remained unclear. Here we have developed and applied a doxycycline-repressible allele of galactokinase to define the quantitative relationship between galactokinase activity, gal-1P accumulation, and growth arrest of galactose-challenged GALT or GALE-deficient yeast. Our results demonstrate a clear threshold relationship between gal-1P accumulation and galactose-mediated growth arrest in both GALT-null and GALE-null yeast, however, the threshold for the two strains is distinct. Further, we tested the galactose-sensitivity of yeast double-null for GALT and GALE, and found that although loss of GALT barely changed accumulation of gal-1P, it significantly lowered the accumulation of UDP-gal, and also dramatically rescued growth of the GALE-null cells. Together, these data suggest that while gal-1P alone may account for the galactose-sensitivity of GALT-null cells, other factors, likely to include UDP-gal accumulation, must contribute to the galactose-sensitivity of GALE-null cells.
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Affiliation(s)
- Jane Odhiambo Mumma
- Department of Human Genetics, Emory University School of Medicine, Emory University, Atlanta, GA
| | - Juliet S. Chhay
- Department of Human Genetics, Emory University School of Medicine, Emory University, Atlanta, GA
| | - Kerry L. Ross
- Department of Human Genetics, Emory University School of Medicine, Emory University, Atlanta, GA
| | - Jana S. Eaton
- Graduate Program in Genetics and Molecular Biology, Emory University, Atlanta, GA
| | - Karen A. Newell-Litwa
- Graduate Program in Biochemistry, Cell, and Developmental Biology, Emory University, Atlanta, GA
| | - Judith L. Fridovich-Keil
- Department of Human Genetics, Emory University School of Medicine, Emory University, Atlanta, GA
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Jama M, Nelson L, Pont-Kingdon G, Mao R, Lyon E. Simultaneous amplification, detection, and analysis of common mutations in the galactose-1-phosphate uridyl transferase gene. J Mol Diagn 2007; 9:618-23. [PMID: 17884932 PMCID: PMC2049049 DOI: 10.2353/jmoldx.2007.070027] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Classic galactosemia is an autosomal recessive inherited error of galactose metabolism. It is caused by lack of galactose-1-phosphate uridyl transferase, an enzyme that is required to metabolize galactose-1-phosphate to uridine diphosphate galactose. The build up of galactose-1-phosphate is toxic at high levels and can damage the liver, brain, eyes, and other vital organs. Over 200 mutations have been identified in affected individuals. We describe an assay to identify nine target mutations or variants in the galactose-1-phosphate uridyl transferase gene, namely p.Q188R, p.S135L, p.K285N, p.L195P, p.T138M, p.Y209C, IVS2-2 A>G, p.L218L, and p.N314D. A single long-range PCR is followed by a multiplexed nucleotide extension assay (single nucleotide extension) and capillary electrophoresis to detect simultaneously all nine target mutations/variants. Fifty-four previously characterized samples (47 clinical samples and seven controls) gave a 100% concordance. We also report a nontarget novel mutation, p.L192X, and its profile using single nucleotide extension. This assay can complement the enzyme activity assay and identify familial mutations for testing additional family members.
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Affiliation(s)
- Mohamed Jama
- ARUP Institute for Clinical and Experimental Pathology, 500 Chipeta Way, Salt Lake City, UT 84108, USA
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Dai N, Petreikov M, Portnoy V, Katzir N, Pharr DM, Schaffer AA. Cloning and expression analysis of a UDP-galactose/glucose pyrophosphorylase from melon fruit provides evidence for the major metabolic pathway of galactose metabolism in raffinose oligosaccharide metabolizing plants. Plant Physiol 2006; 142:294-304. [PMID: 16829585 PMCID: PMC1557607 DOI: 10.1104/pp.106.083634] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The Cucurbitaceae translocate a significant portion of their photosynthate as raffinose and stachyose, which are galactosyl derivatives of sucrose. These are initially hydrolyzed by alpha-galactosidase to yield free galactose (Gal) and, accordingly, Gal metabolism is an important pathway in Cucurbitaceae sink tissue. We report here on a novel plant-specific enzyme responsible for the nucleotide activation of phosphorylated Gal and the subsequent entry of Gal into sink metabolism. The enzyme was antibody purified, sequenced, and the gene cloned and functionally expressed in Escherichia coli. The heterologous protein showed the characteristics of a dual substrate UDP-hexose pyrophosphorylase (PPase) with activity toward both Gal-1-P and glucose (Glc)-1-P in the uridinylation direction and their respective UDP-sugars in the reverse direction. The two other enzymes involved in Glc-P and Gal-P uridinylation are UDP-Glc PPase and uridyltransferase, and these were also cloned, heterologously expressed, and characterized. The gene expression and enzyme activities of all three enzymes in melon (Cucumis melo) fruit were measured. The UDP-Glc PPase was expressed in melon fruit to a similar extent as the novel enzyme, but the expressed protein was specific for Glc-1-P in the UDP-Glc synthesis direction and did not catalyze the nucleotide activation of Gal-1-P. The uridyltransferase gene was only weakly expressed in melon fruit, and activity was not observed in crude extracts. The results indicate that this novel enzyme carries out both the synthesis of UDP-Gal from Gal-1-P as well as the subsequent synthesis of Glc-1-P from the epimerase product, UDP-Glc, and thus plays a key role in melon fruit sink metabolism.
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Affiliation(s)
- Nir Dai
- Department of Vegetable Research, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Israel
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11
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He C, Song Y, He X, Zhang W, Liao L. No association of endometriosis with galactose-1-phosphate uridyl transferase mutations in a Chinese population. Environ Mol Mutagen 2006; 47:307-9. [PMID: 16416427 DOI: 10.1002/em.20200] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The linkage between endometriosis and galactose-1-phosphate uridyl transferase gene (GALT) mutations is controversial. In this study, the prevalence of the most common GALT mutations, Q188R and N314D, was assessed in women with endometriosis in a Chinese population. Three hundred twenty five unrelated women with endometriosis were enrolled. Samples of umbilical cord blood obtained from 310 female newborn infants were used as population controls. Genomic DNA isolated from endometriosis patients and controls were subjected to multiple polymerase chain reactions to determine the Q188R and N314D mutations. There was no significant difference in the frequencies of the Q188R and N314D mutations between endometriosis patients and controls. The endometriosis patients were further divided into subgroups of stage III and IV disease, but still no statistically significant differences were observed in the frequency of the Q188R and N314D mutations between any of these groups and the controls. These findings suggest that Q188R and N314D mutations are not likely to be associated with an increased risk of endometriosis among Chinese Women.
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Affiliation(s)
- Chunni He
- Department of Obstetrics and Gynecology, Fuzhou General Hospital, Fuzhou, People's Republic of China
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12
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Yoshida S, Steele J, Koninckx J, McVeigh E, Kennedy S. The Duarte (N314D) variant in the GALT gene has no effect on in vitro fertilization outcome. Fertil Steril 2006; 85:502-4. [PMID: 16595241 DOI: 10.1016/j.fertnstert.2005.07.1307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2005] [Revised: 07/18/2005] [Accepted: 07/18/2005] [Indexed: 11/16/2022]
Abstract
We assessed the effect of the Duarte (N314D) variant in the GALT gene on in vitro fertilization outcome measures. Our data do not definitely exclude variants in the GALT gene as factors influencing outcome, but the lack of suggestive evidence makes it difficult to justify a larger, more definitive study.
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Affiliation(s)
- Shigeki Yoshida
- Nuffield Department of Obstetrics and Gynaecology, University of Oxford, Oxford, United Kingdom.
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Lebea PJ, Pretorius PJ. The molecular relationship between deficient UDP-galactose uridyl transferase (GALT) and ceramide galactosyltransferase (CGT) enzyme function: A possible cause for poor long-term prognosis in classic galactosemia. Med Hypotheses 2005; 65:1051-7. [PMID: 16125333 DOI: 10.1016/j.mehy.2005.06.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2005] [Revised: 06/09/2005] [Accepted: 06/10/2005] [Indexed: 11/18/2022]
Abstract
Classic galactosemia is an autosomal recessive disorder that is caused by activity deficiency of the UDP-galactose uridyl transferase (GALT). The clinical spectrum of classic galactosemia differs according to the type and number of mutations in the GALT gene. Short-term clinical symptoms such as jaundice, hepatomegaly, splenomegaly and E. coli sepsis are typically associated with classic galactosemia. These symptoms are often severe but quickly ameliorate with dietary restriction of galactose. However, long-term symptoms such as mental retardation and primary ovarian failure do not resolve irrespective of dietary intervention or the period of initial dietary intervention. There seem to be an association between deficient galactosylation of cerebrosides and classic galactosemia. Galactocerebrosides and glucocerebrosides are the primary products of the enzyme UDP-galactose:cerebroside galactosyl transferase (CGT). There has been an observation of deficient galactosylation coupled with over glucosylation in the brain tissue specimens sampled from deceased classic galactosemia patients. The plausible mechanism with which the association between GALT and CGT had not been explained before. Yet, UDP-galactose serves as the product of GALT as well as a substrate for CGT. In classic galactosemia, there is a consistent deficiency in cerebroside galactosylation. We postulate that the molecular link between defective GALT enzyme, which result in classic galactosemia; and the cerebroside galactosyl transferase, which is responsible for galactosylation of cerebrosides is dependent on the cellular concentrations of UDP-galactose. We further hypothesize that a threshold concentration of UDP-galactose exist below which the integrity of cerebroside galactosylation suffers.
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Affiliation(s)
- Phiyani Justice Lebea
- Biotechnology Section, Department of Health Sciences, Vaal University of Technology, Block F110, Andries Potgieter Boulevard, Vanderbijlpark 1900, South Africa.
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15
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Seiboth B, Hartl L, Pail M, Fekete E, Karaffa L, Kubicek CP. The galactokinase of Hypocrea jecorina is essential for cellulase induction by lactose but dispensable for growth on d-galactose. Mol Microbiol 2004; 51:1015-25. [PMID: 14763977 DOI: 10.1046/j.1365-2958.2003.03901.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Lactose is the only soluble carbon source which can be used economically for the production of cellulases or heterologous proteins under cellulase expression signals by Hypocrea jecorina (=Trichoderma reesei). Towards an understanding of lactose metabolism and its role in cellulase formation, we have cloned and characterized the gal1 (galactokinase) gene of H. jecorina, which catalyses the first step in d-galactose catabolism. It exhibits a calculated Mr of 57 kDa, and shows moderate identity (about 40%) to its putative homologues of Saccharomyces cerevisiae and Kluyveromyces lactis. Gal1 is a member of the GHMP family, shows conservation of a Gly/Ser rich region involved in ATP binding and of amino acids (Arg 51, Glu 57, Asp 60, Asp 214, Tyr 270) responsible for galactose binding. A single transcript was formed constitutively during the rapid growth phase on all carbon sources investigated and accumulated to about twice this level during growth on d-galactose, l-arabinose and their corresponding polyols. Deletion of gal1 reduces growth on d-galactose but does only slightly affect growth on lactose. This is the result of the operation of a second pathway for d-galactose catabolism, which involves galactitol as an intermediate, and whose transient concentration is strongly enhanced in the delta-gal1 strain. In this pathway, galactitol is catabolised by the lad1-encoded l-arabinitol-4-dehydrogenase, because a gal1/lad1 double delta-mutant failed to grow on d-galactose. In the delta-gal1 strain, induction of the Leloir pathway gene gal7 (encoding galactose-1-phosphate uridylyltransferase) by d-galactose, but not by l-arabinose, is impaired. Induction of cellulase gene expression by lactose is also impaired in a gal1 deleted strain, whereas their induction by sophorose (the putative cellulose-derived inducer) was shown to be normal, thus demonstrating that galactokinase is a key enzyme for cellulase induction during growth on lactose, and that induction by lactose and sophorose involves different mechanisms.
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Affiliation(s)
- Bernhard Seiboth
- Division of Gene Technology and Applied Biochemistry, Institute of Chemical Engineering, TU Wein, Vienna, Austria.
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16
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Flanagan JM, Tighe O, O' Neill C, Naughten E, Mayne PD, Croke DT. Identification of sequence variation in the galactose-1-phosphate uridyl transferase gene by dHPLC. Mol Genet Metab 2004; 81:133-6. [PMID: 14741195 DOI: 10.1016/j.ymgme.2003.10.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Transferase-deficient galactosaemia is an inherited disorder of carbohydrate metabolism, caused by mutation at the galactose-1-phosphate uridyl transferase (GALT) locus. A denaturing high performance liquid chromatography (dHPLC) method was developed for variant scanning of the GALT gene. The method unequivocally identified the Duarte D1, D2, Q188R, and K285N GALT alleles and associated polymorphisms. Length polymorphism in an intronic Alu repeat was characterised and a novel Single Nucleotide Polymorphism (IVS10nt-322g-->t) associated with the D1 allele was identified.
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Affiliation(s)
- Jonathon M Flanagan
- Department of Pathology, The Children's University Hospital, Temple Street, Dublin 1, Ireland
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17
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Abstract
In humans, the absence of galactose-1-phosphate uridyltransferase (GALT) leads to significant neonatal morbidity and mortality which are dependent on galactose ingestion, as well as long-term complications of primary ovarian failure and cognitive dysfunction, which are diet independent. The creation of a knockout mouse model for GALT deficiency was aimed at providing an organism in which metabolic challenges and gene manipulation could address the enigmatic pathophysiologic questions raised by humans with galactosemia. Instead, the mouse represents a biochemical phenotype without evidence of clinical morbidity. The similarities and differences between mice and humans with galactosemia are explored from metabolite, enzyme, and process points of view. The mouse both produces and oxidizes galactose in a manner similar to humans. It differs in brain accumulation of galactitol. Future directions for exploration of this enigmatic condition are discussed.
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Affiliation(s)
- Nancy D Leslie
- Division of Human Genetics, Cincinnati Children's Hospital Research Foundation, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA.
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18
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Abstract
RNA editing produces mature trypanosome mitochondrial mRNAs by uridylate (U) insertion and deletion. In insertion editing, Us are added to the pre-mRNA by a 3' terminal uridylyl transferase (TUTase) activity. We report the identification of a TUTase activity that copurifies with in vitro editing and is catalyzed by the integral editosome protein TbMP57. TbMP57 catalyzes the addition of primarily a single U to single-stranded (ss) RNA and adds the number of Us specified by a guide RNA to insertion editing-like substrates. TbMP57 is distinct from a previously identified TUTase that adds many Us to ssRNA and which we find is neither a stable editosome component nor does it add Us to editing-like substrates. Recombinant TbMP57 specifically interacts with the editosome protein TbMP81, and this interaction enhances the TUTase activity. These results suggest that TbMP57 catalyzes U addition to pre-mRNA during editing.
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MESH Headings
- Animals
- Catalysis
- Chromatography, Agarose
- Chromatography, Gel
- Chromatography, Ion Exchange
- Mitochondria/chemistry
- Mitochondria/enzymology
- Molecular Sequence Data
- Molecular Weight
- Protein Structure, Tertiary
- Protozoan Proteins
- RNA/genetics
- RNA/metabolism
- RNA Editing
- RNA Precursors/genetics
- RNA Precursors/metabolism
- RNA, Guide, Kinetoplastida/chemistry
- RNA, Guide, Kinetoplastida/genetics
- RNA, Guide, Kinetoplastida/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Recombinant Proteins/metabolism
- Ribonucleoproteins/metabolism
- Substrate Specificity
- Trypanosoma brucei brucei/cytology
- Trypanosoma brucei brucei/enzymology
- Trypanosoma brucei brucei/genetics
- UDPglucose-Hexose-1-Phosphate Uridylyltransferase/genetics
- UDPglucose-Hexose-1-Phosphate Uridylyltransferase/isolation & purification
- UDPglucose-Hexose-1-Phosphate Uridylyltransferase/metabolism
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19
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Dobrowolski SF, Banas RA, Suzow JG, Berkley M, Naylor EW. Analysis of common mutations in the galactose-1-phosphate uridyl transferase gene: new assays to increase the sensitivity and specificity of newborn screening for galactosemia. J Mol Diagn 2003; 5:42-7. [PMID: 12552079 PMCID: PMC1907369 DOI: 10.1016/s1525-1578(10)60450-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Classical galactosemia is a genetic disease caused by mutations in the galactose-1-phosphate uridyl transferase (GALT) gene. Prospective newborn screening for galactosemia is routine and utilizes the universally collected newborn dried blood specimen on filter paper. Screening for galactosemia is achieved through analysis of total galactose (galactose and galactose-1-phosphate) and/or determining the activity of the GALT enzyme. While this approach is effective, environmental factors and the high frequency of the Duarte D2 mutation (N314D) does lead to false positive results. Using DNA derived from the original newborn dried blood specimen and Light Cycler technology a panel of five assays able to detect the four most frequently encountered classical galactosemia alleles (Q188R, S135L, K285N, and L195P) and the N314D Duarte variant mutation are described. The five assays are performed simultaneously using common conditions. Including DNA preparation, set-up, amplification, and analysis the genotype data for all five loci is obtained in less than 2 hours. The assays are easily interpreted and amenable to high-throughput newborn screening. Mutational analysis is useful to reduce false positive results, differentiate D/G mixed heterozygotes from classical galactosemia, and to clearly identify a very high percentage of those affected by classical galactosemia.
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20
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Grossiord BP, Luesink EJ, Vaughan EE, Arnaud A, de Vos WM. Characterization, expression, and mutation of the Lactococcus lactis galPMKTE genes, involved in galactose utilization via the Leloir pathway. J Bacteriol 2003; 185:870-8. [PMID: 12533462 PMCID: PMC142802 DOI: 10.1128/jb.185.3.870-878.2003] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2002] [Accepted: 11/06/2002] [Indexed: 11/20/2022] Open
Abstract
A cluster containing five similarly oriented genes involved in the metabolism of galactose via the Leloir pathway in Lactococcus lactis subsp. cremoris MG1363 was cloned and characterized. The order of the genes is galPMKTE, and these genes encode a galactose permease (GalP), an aldose 1-epimerase (GalM), a galactokinase (GalK), a hexose-1-phosphate uridylyltransferase (GalT), and a UDP-glucose 4-epimerase (GalE), respectively. This genetic organization reflects the order of the metabolic conversions during galactose utilization via the Leloir pathway. The functionality of the galP, galK, galT, and galE genes was shown by complementation studies performed with both Escherichia coli and L. lactis mutants. The GalP permease is a new member of the galactoside-pentose-hexuronide family of transporters. The capacity of GalP to transport galactose was demonstrated by using galP disruption mutant strains of L. lactis MG1363. A galK deletion was constructed by replacement recombination, and the mutant strain was not able to ferment galactose. Disruption of the galE gene resulted in a deficiency in cell separation along with the appearance of a long-chain phenotype when cells were grown on glucose as the sole carbon source. Recovery of the wild-type phenotype for the galE mutant was obtained either by genetic complementation or by addition of galactose to the growth medium.
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Affiliation(s)
- Benoît P Grossiord
- NIZO Food Research, 6710 BA Ede. Laboratory of Microbiology, Wageningen University, 6703 CT Wageningen, The Netherlands.
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21
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Abstract
In order to assess the pathways by which galactose is metabolized by galactose-1-phosphate uridyltransferase (GALT) deficient cells, lymphoblasts from 10 galactosemic patients with defined genotypes (six Q188R homozygotes, two S153L homozygotes, and two with homozygous deletions) were incubated with 1mM 1- or 2-13C galactose for 2.5 and 5 h. The 13C-labeled metabolites were identified and quantified using nuclear magnetic resonance and the results were compared to that obtained with cells from eight normal individuals. Cells from galactosemic patients formed two to three times the galactose-1-phosphate (Gal-1P) in normal cells, no difference being observed between the various genotypes. Galactitol formation was not significantly different from normal cells. No labeled galactonate was detected. Cells with the Q188R and S135L mutations formed both labeled uridine diphosphogalactose (UDPgal) and uridine diphosphoglucose (UDPglu), but to a lesser extent than normals, whereas cells with the GALT deletion did not. The pattern of 13C enrichment of the ribose carbons of adenosine monophosphate upon incubation of the normal cells with 1-13C galactose paralleled that found for incubations with 1-13C glucose, which is consistent with galactose disposition through the Leloir pathway to glucose and its subsequent metabolism to ribose. Cells with the GALT deletion formed no detectable labeled ribose, whereas cells from a patient homozygous for Q188R mutation formed labeled ribose in a pattern similar to normal albeit with lower enrichment. The results suggest that there is residual GALT activity and function of the Leloir pathway in the presence of the Q188R as well as S135L mutation.
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Affiliation(s)
- Suzanne L Wehrli
- NMR Core Facility, Joseph Stokes Jr. Research Institute, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
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22
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Abstract
Impairment of the human enzyme galactose-1-P uridylyltransferase (hGALT) results in the potentially lethal disorder, galactosemia. One of the fundamental questions with regard to this dimeric enzyme involves the possible influence of patient mutations on heterodimer formation and activity. Indeed, considering that many if not most galactosemia patients are compound heterozygotes, this is an issue of clinical as well as basic science interest. We have utilized a yeast expression system for the human enzyme to test whether each of a small number of mutations in hGALT (S135L, F171S, F171W, Q188R, N314D, and R333W) impact either heterodimer formation or function. Our results clearly demonstrate that while a majority of the alleles tested show precisely random patterns of subunit assortment, two deviate slightly but significantly from this pattern. Similarly, while some heterodimers exhibit apparent independence of subunit activity, others do not. These data not only demonstrate that common patient mutations in hGALT can influence both heterodimer formation and function in heterozygotes, they further raise the question of whether such interactions may also occur between different mutant alleles in compound heterozygotes (i.e., patients). Indeed, such influences may underlie some of the biochemical and clinical heterogeneity observed in the galactosemia patient population.
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Affiliation(s)
- Nicole C Christacos
- Graduate Program in Genetics and Molecular Biology, Emory University, Atlanta, GA, USA
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23
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Abstract
Nucleotide excision repair (NER) and transcription are intimately related. First, TFIIH has a dual role in transcription initiation and NER and, secondly, transcription leads to more efficient repair of damage present in transcribed sequences. It is thought that elongating RNAPII, stalled at a DNA lesion, is used for the loading of the NER machinery in a process termed transcription-coupled repair (TCR). Non-transcribed regions are repaired by the so-called global genome repair (GGR). We have previously defined a number of yeast genes, whose deletions confer transcription-dependent hyper-recombination phenotypes. As these mutations cause impairment of transcription elongation we have assayed whether they also affect DNA repair. We show that null mutations of the HPR1 and THO2 genes, encoding two prominent proteins of the THO complex, increase UV sensitivity of yeast cells lacking GGR. Consistent with this result, molecular analyses of DNA repair of the RPB2 transcribed strand using T4 endo V show that hpr1 and tho2 do indeed impair TCR. However, this effect is not confined to TCR alone because the mutants are slightly affected in GGR. These results indicate that THO affects both transcription and NER. We discuss different alternatives to explain the effect of the THO complex on DNA repair.
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MESH Headings
- Blotting, Northern
- Cell Cycle Proteins
- DNA Repair/genetics
- DNA, Fungal/genetics
- DNA, Fungal/metabolism
- DNA, Fungal/radiation effects
- DNA-Binding Proteins
- Deoxyribonuclease (Pyrimidine Dimer)
- Dose-Response Relationship, Radiation
- Endodeoxyribonucleases/metabolism
- Fungal Proteins/genetics
- Gene Expression Regulation, Fungal/radiation effects
- Genotype
- Mating Factor
- Mutation
- Nuclear Proteins
- Peptides/genetics
- Protein Subunits
- RNA Polymerase II/genetics
- RNA, Fungal/genetics
- RNA, Fungal/metabolism
- RNA, Fungal/radiation effects
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/radiation effects
- Saccharomyces cerevisiae Proteins
- Schizosaccharomyces pombe Proteins
- Transcription Factors/genetics
- Transcription, Genetic
- UDPglucose-Hexose-1-Phosphate Uridylyltransferase/genetics
- Ultraviolet Rays
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Affiliation(s)
- Sergio González-Barrera
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Avd. Reina Mercedes 6, 41012 Sevilla, Spain
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24
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Abstract
Small nucleolar RNAs represent an abundant, evolutionarily ancient group of noncoding RNAs which possess impressively diverse functions ranging from 2'-O-methylation and pseudouridylation of various classes of RNAs, through nucleolytic processing of rRNAs to the synthesis of telomeric DNA.
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Affiliation(s)
- Tamás Kiss
- Laboratoire de Biologie Moléculaire Eucaryote du CNRS, Université Paul Sabatier, 118 route de Narbonne, 31062 Cedex, Toulouse, France.
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25
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Item C, Hagerty BP, Mühl A, Greber-Platzer S, Stöckler-Ipsiroglu S, Strobl W. Mutations at the galactose-1-p-uridyltransferase gene in infants with a positive galactosemia newborn screening test. Pediatr Res 2002; 51:511-6. [PMID: 11919338 DOI: 10.1203/00006450-200204000-00018] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Newborn screening for galactosemia yields a high number of false-positive results. Confirmatory DNA testing for unknown galactosemia mutations on the initial positive sample using novel techniques of mutation detection tenders itself to reduce the recall rate. The potential benefits of confirmatory DNA testing, however, could be offset by the detection of a high percentage of galactosemia carriers, Duarte/galactosemia compound heterozygotes, and infants with benign sequence changes in the galactose-1-phosphate uridyltransferase (GALT) gene among infants with a positive biochemical screening test. Our aim was to determine the frequency and allelic distribution of all sequence changes in the GALT gene in 110 newborns with a positive total galactose screening test among 43,688 Austrian newborns screened consecutively. We found that only 20 of the 110 probands carried at least one known or novel candidate galactosemia mutation (one galactosemia homozygote, 7 Duarte/galactosemia compounds, 12 carriers) as judged by denaturing gradient gel electrophoresis and cleavage fragment length polymorphism analysis. Four novel galactosemia candidate mutations (Q9H, A46fsdelCAGCT, M129T, L342I) were identified. Sixty-seven probands had no detectable sequence changes and 23 carried only the benign Duarte or Los Angeles variant alleles or silent mutations. We conclude that a rapid and automatable confirmation test for unknown GALT mutations, e.g. on a high-density oligonucleotide array basis, has the potential to lower the recall rate of galactosemia screening in our population by about five-fold from 0.25 to 0.046%. Further research, however, will be required before the development of such a test can be advocated.
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Affiliation(s)
- Chike Item
- Department of Pediatrics, University of Vienna, Austria
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26
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Seiboth B, Hofmann G, Kubicek CP. Lactose metabolism and cellulase production in Hypocrea jecorina: the gal7 gene, encoding galactose-1-phosphate uridylyltransferase, is essential for growth on galactose but not for cellulase induction. Mol Genet Genomics 2002; 267:124-32. [PMID: 11919723 DOI: 10.1007/s00438-002-0654-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2001] [Accepted: 01/30/2002] [Indexed: 10/27/2022]
Abstract
Lactose is at present the only soluble carbon source which can be used economically for the production by Hypocrea jecorina (= Trichoderma reesei) of cellulases or heterologous proteins under the control of cellulase expression signals. However, the mechanism by which lactose triggers the formation of cellulases is unknown. To enhance our understanding of lactose metabolism and its relationship to cellulase formation, we have cloned and characterized the gal7 gene (for galactose-1-phosphate uridylyltransferase) of H. jecorina. The gene encodes a polypeptide of 43.8 kDa, the sequence of which exhibits a moderate level of identity (about 50%) to that of the Gal7 proteins of Saccharomyces cerevisiae and Kluyveromyces lactis, and contains an active-site signature typical for galactose-1-phosphate uridylyltransferase family 1. H. jecorina gal7 is not clustered with other genes of galactose metabolism. A single 1.7-kb transcript is synthesized constitutively during the rapid growth phase and accumulated to twice this level during incubation in the presence of D-galactose and L-arabinose and the corresponding polyols (dulcitol, arabitol). A gal7 deletion mutant, constructed by replacing the gal7 reading frame by the H. jecorina pyr4 gene, was unable to grow on D-galactose between pH 4.5 and 7.5, thus proving that in H. jecorina gal7 is essential for metabolism of D-galactose, whereas the growth rate of the mutant on lactose was only reduced by about 50%. The rate of formation of cellobiohydrolase Cel7A and the abundance of the corresponding (cbh1) transcript during growth on lactose was only slightly lower in the absence of gal7, but a significant delay in decay of the cbh1 transcript was noted during later stages of growth. The results suggest that H. jecorina uses only the Leloir pathway for metabolism of D-galactose and lactose. Furthermore, we conclude that metabolism of lactose past the galactose-1-phosphate step is not essential for cellulase formation.
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Affiliation(s)
- B Seiboth
- Bereich Mikrobielle Biochemie und Gentechnologie, Institut für Biochemische Technologie und Mikrobiologie, Technische Universität Wien, Getreidemarkt 9, A-1060 Vienna, Austria.
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27
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Abstract
The spectrum of mutations in the Galactose-1-phosphate uridyl transferase (GALT) gene is described in 11 cases of classic galactosemia and 38 of Duarte-2 type identified by the Texas Newborn Screening Program. Blinded studies were done by automated DNA sequencing of all the 11 exons and the exon-intron boundaries of the GALT gene using genomic DNA isolated from dry blood spots. Fourteen different mutations (11 missense mutations, 2 nonsense mutations and 1 splicing mutation) were detected in 94 of the 98 mutant alleles (diagnostic efficiency of 96%). The prevalent mutations were N314D (41%), Q188R (37%) and K285N (4%). The other less frequent mutations were IVS2-2A>G and S135L (3% each), T138M (2%) and T23A, H184Q, Y251S, L195P, Q207X, L264X, Q344K, and A345D (1% each). Three novel mutations, T23A, Q207X, and A345D, were identified. Our study supports previous findings that N314D and Q188R are prevalent in Hispanics and Whites and K285N was only observed in Whites. The IVS2-2A->G mutation is probably ethnic specific because it was identified exclusively in Hispanics. S135L, a prevalent mutation in Blacks, was also present in 3 Hispanics. Two unusual genotypes were observed in 2 patients homozygous for the Duarte-2 N314D allele and heterozygous for a novel mutation (Q207X- N314D/N314D in a classic galactosemia and T23A- N314D/N314D in a Duarte-2 case). The detection of GALT gene mutations in newborns from Texas should focus first on N314D, Q188R, K285N, IVS2-2A>G, S135L and T138M. Other exons and exon-intron boundaries would have to be studied if either one or no mutations are found in the primary screening.
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Affiliation(s)
- Y P Yang
- Genetic Testing Center, Texas Department of Health, 3600 E. McKinney St., Denton, TX 76209, USA
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28
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Abstract
We previously identified a missense mutation at amino acid 135 of human galactose 1-phosphate uridyltransferase (hGALT) in which a leucine (TTG) was substituted for a serine (TCG), S135L. This mutation was common in black patients with galactosemia and homozygotes (S135L/S135L) had no GALT activity or protein in their erythrocytes or lymphoblasts. However, there was residual GALT activity and protein in their leukocytes, and they had near normal total body [13C]galactose oxidation to 13CO2 in breath. To evaluate the biochemical mechanism(s) producing these effects, we overexpressed hGALT proteins with site-directed mutations in this nonconserved amino acid in a GALT-minus Escherichia coli. Enzyme activities detected in bacterial lysates overexpressing either S135 (wild type), A135, C135, H135, L135, S132-H135, T135, or Y135 were 100, 4.7, 3.0, 4.0, 2.7, 0.7, 35.4, and 1.4%, respectively. Only the threonine substitution (S135T) had significant enzyme activity in these lysates. There was also decreased abundance of all mutant proteins in the lysates exposed to bacterial proteolysis during preparation and analysis. This added the variable of bio-instability to analysis of enzyme activities in lysates. To further characterize the catalytic role of serine at amino acid 135 and to differentiate bio-instability from impaired catalysis by the leucine substitution, we purified wild-type and L135-hGALT proteins to homogeneity and analyzed identical amounts of enzyme protein. We found that the apparent Vmax of the purified L135-hGALT protein was significantly reduced from 80 +/- 5.9 to 5.8 +/- 1.8 micromol glucose 1-phosphate released/min/mg hGALT protein with no increase in KM for galactose 1-phosphate for the second displacement. The first displacement reaction, although three orders of magnitude slower, was similar between the wild type and L135-hGALT. We conclude that a hydroxyl group on amino acid 135 is required for the catalysis of uridyl transfer from UDP-glucose to UDP-galactose in the presence of galactose 1-phosphate, and plays a role in the bio-stability of hGALT.
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Affiliation(s)
- K Lai
- Division of Medical Genetics, Department of Pediatrics, Emory University School of Medicine, 2040 Ridgewood Drive, Atlanta, Georgia 30322, USA
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29
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Abstract
This paper (i) reviews the current clinical and molecular genetic data which strongly suggest that endometriosis has a genetic basis; (ii) outlines the general principles of affected-sib pair analysis; and (iii) describes the Oxford Endometriosis Gene (OXEGENE) Study which aims, using a positional cloning approach, to identify susceptibility genes involved in the development of the disease.
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Affiliation(s)
- S Kennedy
- Nuffield Department of Obstetrics and Gynaecology, University of Oxford, UK.
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30
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Abstract
The ability of mice deficient in galactose-1-phosphate uridyltransferase (GALT) to metabolize galactose was determined in animals weaned to a mouse chow diet for a 4-wk period. When given [14C]galactose intraperitoneally, these animals slowly oxidized the sugar, excreting only 5.5% of the dose as 14CO2 in 4 h, whereas normal animals excreted 39.9%. These results mimic those seen in human galactosemic patients given isotopic galactose. When given 10 micromol of [1-13C]galactose, normal animals excrete small amounts of labeled galactose and galactonate but no galactitol in urine whereas GALT-deficient mice excrete significant amounts of all of these as labeled compounds in urine. When challenged with galactose, only about 20% of the dose is excreted in urine, and even on the chow diet, significant amounts of galactose, galactonate, and galactitol are excreted in urine. These compounds are also found to be present in liver, kidney, and brain, except that galactonate is not found in brain. Galactose-1-phosphate accumulates in red blood cells to levels found in humans exposed to large amounts of galactose, and galactose-1-phosphate is found in increased amounts in liver, kidney, and brain of GALT-deficient animals. There was no difference in the hepatic concentration of uridine diphosphate galactose and uridine diphosphate glucose between normal and GALT-deficient mice. The explanation for the presence of galactose and its conversion products in tissues and urine of affected mice appears to be related to the presence of approximately 1.75% of galactose-containing carbohydrates in the chow, which becomes bioavailable to mice. Despite the presence of galactose and its metabolites in tissues and urine and impaired ability to oxidize the sugar, the GALT-deficient animals are indistinguishable from normal animals and do not exhibit the phenotype of humans with GALT-deficiency galactosemia.
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Affiliation(s)
- C Ning
- Division of Biochemical Development and Molecular Diseases, The Children's Hospital of Philadelphia,Pennsylvania 19104, USA
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31
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Geeganage S, Frey PA. Significance of metal ions in galactose-1-phosphate uridylyltransferase: an essential structural zinc and a nonessential structural iron. Biochemistry 1999; 38:13398-406. [PMID: 10529216 DOI: 10.1021/bi9910631] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Galactose-1-phosphate uridylyltransferase (GalT) catalyzes the reversible transformation of UDP-glucose and galactose-1-phosphate (Gal-1-P) into UDP-galactose and glucose-1-phosphate (Glc-1-P) by a double displacement mechanism, with the intermediate formation of a covalent uridylyl-enzyme (UMP-enzyme). GalT is a metalloenzyme containing 1.2 mol of zinc and 0.7 mol of iron/mol of subunits [Ruzicka, F. J., Wedekind, J. E., Kim, J., Rayment, I., and Frey, P. A. (1995) Biochemistry 34, 5610-5617]. The zinc site lies 8 A from His 166 in active site, and the iron site lies 30 A from the active site [Wedekind,J. E., Frey, P. A., & Rayment, I. (1995) Biochemistry 34, 11049-11061]. Zinc is coordinated in tetrahedral geometry by Cys 52, Cys 55, His 115, and His 164. His 164 is part of the highly conserved active-site triad His 164-Pro 165-His 166, in which His 166 is the nucleophilic catalyst. Iron is coordinated in square pyramidal geometry with His 296, His 298, and Glu 182 in bidentate coordination providing the base ligands and His 281 providing the axial ligand. In the present study, site-directed mutagenesis, kinetic, and metal analysis studies show that C52S-, C55S-, and H164N-GalT are 3000-, 600-, and 10000-fold less active than wild-type. None of the variants formed the UMP-enzyme in detectable amounts upon reaction with UDP-Glc in the absence of Gal-1-P. Their zinc content was very low, and the zinc + iron content was about 50% of that for wild-type GalT. Mutation of His 115 to Asn 115 resulted in decreased activity to 2.9% of wild-type, with retention of zinc and iron. In contrast to the zinc-binding site, Glu 182 in the iron site is not important for enzymatic activity. The variant E182A-GalT displayed about half the activity of wild-type GalT, and all of the active sites underwent uridylylation to the UMP-enzyme, similar to wild-type GalT, upon reaction with UDP-Glc. Metal analysis showed that while E182A-GalT contained 0.9 equiv of zinc/subunit, it contained no iron. The residual zinc can be removed by dialysis with 1,10-phenanthroline, with the loss in activity being proportional to the amount of residual zinc. It is concluded that the presence of zinc is essential for maintaining GalT function, whereas the presence of iron is not essential.
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Affiliation(s)
- S Geeganage
- Institute for Enzyme Research, The Graduate School, Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison 53705, USA
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32
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Hadfield RM, Manek S, Nakago S, Mukherjee S, Weeks DE, Mardon HJ, Barlow DH, Kennedy SH. Absence of a relationship between endometriosis and the N314D polymorphism of galactose-1-phosphate uridyl transferase in a UK population. Mol Hum Reprod 1999; 5:990-3. [PMID: 10508229 DOI: 10.1093/molehr/5.10.990] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
An association between the N314D polymorphism of galactose-1-phosphate uridyl transferase and endometriosis has recently been reported in a North American population. To determine whether such an association exists in the UK population, we genotyped 148 women with sporadic (n = 91) or familial (n = 57) endometriosis, a control population of 95 male blood donors and a control group of 53 women with a normal pelvis at hysterectomy. Heterozygosity for the polymorphism was found in 14.9% (22/148) of affected women, 13.7% (13/95) of male blood donors and 11.3% (6/53) of women with a normal pelvis. There was no statistically significant difference in the frequency of the polymorphism between cases and controls in the UK population, even when the cases were divided into groups of moderate-severe disease, sporadic cases or familial cases. We conclude that the galactose-1-phosphate uridyl transferase N314D polymorphism is unlikely to be associated with endometriosis in the UK population.
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Affiliation(s)
- R M Hadfield
- Nuffield Department of Obstetrics & Gynaecology, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK
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33
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Geeganage S, Frey PA. Transient kinetics of formation and reaction of the uridylyl-enzyme form of galactose-1-P uridylyltransferase and its Q168R-variant: insight into the molecular basis of galactosemia. Biochemistry 1998; 37:14500-7. [PMID: 9772178 DOI: 10.1021/bi9815546] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Galactose-1-phosphate uridylyltransferase catalyzes the reaction of UDP-glucose with galactose 1-phosphate (Gal-1-P) to form UDP-galactose and glucose 1-phosphate (Glc-1-P) through a double displacement mechanism, with the intermediate formation of a covalent uridylyl-enzyme (UMP enzyme). Gln 168 in E. coli uridylyltransferase engages in hydrogen bonding with the phosphoryl oxygens of the UMP moiety, which is bonded to His 166 in the intermediate [Wedekind, J. E., Frey, P. A., and Rayment, I. (1996) Biochemistry 35, 11560-11569]. In humans, the point variant Q188R accounts for 60% of galactosemia cases. The corresponding E. coli variant Q168R has been overexpressed and purified. In preparation for kinetic correlation of Q168R and wild-type uridylyltransferases, we tested the kinetic competence of the wild-type UMP-enzyme. At 4 degreesC, the first-order rate constant for uridylylation by UDP-glucose is 281 +/- 18 s-1, and for deuridylylation it is 226 +/- 10 s-1 with Glc-1-P and 166 +/- 10 s-1 with Gal-1-P. Inasmuch as the overall turnover number at 4 degreesC is 62 s-1, the covalent intermediate is kinetically competent. The variant Q168R is uridylylated by UDP-glucose to the extent of about 65% of the potential active sites. Uridylylation reactions of Q168R with UDP-glucose proceed with maximum first-order rate constants of 2.2 x 10(-)4 s-1 and 4.2 x 10(-)4 s-1 at 4 and 27 degreesC, respectively. In experiments with uridylyl-Q168R and glucose-1-P, the mutant enzyme undergoes deuridylylation with maximum first-order rate constants of 4.8 x 10(-)4 s-1 and 1.68 x 10(-)3 s-1 at 4 and 27 degreesC, respectively. The value of Km for uridylylation of Q168R is slightly higher than for the wild-type enzyme, and for deuridylylation it is similar to the wild-type value. The wild-type enzyme undergoes uridylylation and deuridylyation about 10(6) times faster than Q168R. The wild-type activity in the overall reaction is 1.8 x 10(6) times that of Q168R. The wild-type enzyme contains 1.9 mol of Zn+Fe per mole of subunits, whereas the Q168R-variant contains 1.36 mol of Zn+Fe per mole of subunits. The mutation stabilizes the uridylyl-enzyme by 1.2 kcal mol-1 in comparison to the wild-type enzyme. These results show that the low activity of Q168R is not due to overstabilization of the intermediate or to the absence of structural metal ions. Instead, the main defect is very slow uridylylation and deuridylation.
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Affiliation(s)
- S Geeganage
- Institute for Enzyme Research, Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison 53705, USA
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34
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Ruzicka FJ, Geeganage S, Frey PA. Kinetic mechanism of UDP-hexose synthase, a point variant of hexose-1-phosphate uridylyltransferase from Escherichia coli. Biochemistry 1998; 37:11385-92. [PMID: 9698386 DOI: 10.1021/bi980877z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Galactose-1-phosphate (galactose-1-P) uridylyltransferase from Escherichia coli catalyzes the interconversion of UDP-glucose and galactose-1-P with UDP-galactose and glucose-1-P by a double-displacement mechanism through a uridylyl-enzyme intermediate, in which the uridine-5'-phosphoryl group is covalently bonded to Nepsilon of His 166. The point variant H166G displays a UDP-hexose synthase activity, in that it catalyzes the reaction of uridine 5'-phosphoimidazolide (UMPIm) with glucose-1-P to form UDP-glucose and imidazole. Inasmuch as the wild-type uridylyltransferase catalyzes its cognate reaction with ping-pong kinetics, an intrinsically ordered substrate binding mechanism, the kinetic mechanism of the UDP-hexose synthase activity of H166G became of interest. The synthase activity follows sequential kinetics [Kim, J., Ruzicka, F., and Frey, P. A. (1990) Biochemistry 29, 10590-10593]. In this work, product inhibition patterns for the synthase activity of H166G indicate random equilibrium binding of substrates. Comparison of the synthase activities of the variants H166G and H166A showed that the glycine variant is about 340- and 600-fold more active than the alanine variant in the forward and reverse directions, respectively. The kinetic consequences of varying the amino acid at position 166 were largely kcat effects, with more modest Km effects. Comparison of the synthase activities of these variants with that of the wild-type enzyme in the production of glucose-1-P showed that the loss of the beta-carbon of His 166 in the complex H166G-UMPIm increases the activation energy for uridylyl group transfer by 2.4 kcal mol-1, and the presence of two additional hydrogen atoms in the complex H166A-UMPIm increases the activation energy by 6.2 kcal mol-1. It is concluded that the active site is much less tolerant of additional steric bulk in the locus of the beta-carbon of His 166 than it is of the loss of the beta-carbon. The sensitivities to additional steric bulk around other positions of the His 166-imidazole ring are much less severe, as indicated by the reactivities of methylated analogues of UMPIm in the synthase reaction of H166G. Uridine 5'-phospho-N-methylimidazolide is more reactive as a synthase substrate than UMPIm, and this is attributed to the positive charge of the imidazole ring. The fact that the imidazole ring of the wild-type covalent uridylyl-enzyme retains its proton and is positively charged is supported by the pH-rate profile for hydrolysis of the intermediate.
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Affiliation(s)
- F J Ruzicka
- Institute for Enzyme Research, The Graduate School, College of Agricultural and Life Sciences, University of Wisconsin-Madison 53705, USA
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35
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Abstract
Impairment of the human enzyme galactose-1-phosphate uridylyltransferase (GALT) results in the potentially lethal disorder galactosaemia. The S135L mutation, which accounts for almost 50% of the GALT alleles in galactosaemia patients of African-American descent, has been associated with activities ranging from null to wild-type by different investigators examining cell lysates representing different tissues or model systems. Because of the crude nature of the lysates examined, however, and the absence of quantitative measures concerning GALT abundance in most of those lysates, the available data do not distinguish between differences in GALT enzyme expression/abundance, specific activity, or kinetic constants in these different tissues or systems. In an effort to overcome this uncertainty and investigate the biochemical impact of the S135L substitution on human GALT function under defined conditions, we have overexpressed both wild-type and S135L-mutant GALT sequences in a null-background yeast expression system, and purified both proteins to near homogeneity. Abundance of the wild-type and mutant proteins in crude yeast lysates differed by approximately 2-fold. Kinetic studies of the purified proteins, however, demonstrated that although K(m) values differed by < 2-fold, specific activities differed by 10-fold. Temperature-activity profiles revealed no significant differences, and coprecipitation studies demonstrated that S135L-hGALT subunits remained competent to self-associate in vivo. We conclude that the S135L substitution causes either steric or electrochemical changes sufficiently close to the active site in human GALT to result in partial impairment of the transferase reaction.
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Affiliation(s)
- L Wells
- Graduate Program in Biochemistry and Molecular Biology, Emory University School of Medicine, Atlanta, Georgia, USA
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36
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Abstract
Galactose-1-phosphate uridyl transferase (GALT) deficiency causes classical galactosemia in humans. Mice deficient in this enzyme were created by gene targeting. GALT-deficient mice develop biochemical features similar to those seen in humans with GALT deficiency, but fail to develop the pattern of acute toxicity seen in newborns with classical galactosemia. This study suggests that alternative routes of galactose metabolism are important in the pathogenesis of galactosemia.
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Affiliation(s)
- N D Leslie
- Division of Human Genetics Children's Hospital Research Foundation, Cincinnati, Ohio 45229, USA
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37
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Abstract
A Cryptococcus neoformans galactose auxotroph was created by ultraviolet light mutagenesis and complemented with a C. neoformans genomic library. The translated sequence of the complementing DNA revealed a high degree of similarity to a number of UDP glucose-D-galactose-1-phosphate uridylyltransferases. Expression of C. neoformans GAL7 mRNA followed a pattern similar to Saccharomyces cerevisiae expression; it was first observed within 2.5 min of induction and fully induced by 30 min. The gene was completely repressed in the presence of glucose. The GAL7 promoter was isolated and used to construct a promoter cassette. Two genes were tested in this cassette for galactose regulation by creating GAL7 promoter fusions with their coding regions. MF alpha, which encodes a pheromone, was found to produce filaments only in transformants that were induced by galactose. A second gene, beta-glucuronidase (gusA), which is a commonly used reporter gene, was tested and also found to be expressed. When the GAL7p::GUS fusion was used to quantify inducibility of the GAL7 promoter, the level of enzyme activity was at least 500-fold greater for cells grown in galactose than for cells grown in glucose. The GAL7 promoter is the first inducible promoter characterized in C. neoformans and the GUS gene is the first heterologous gene shown to be expressed in this yeast pathogen.
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Affiliation(s)
- B L Wickes
- Department of Laboratory Medicine, University of California, San Francisco 94143-0626, USA
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38
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Abstract
The glnD gene in enteric bacteria encodes a uridylyltransferase/uridylyl-removing enzyme which acts as the primary nitrogen sensor in the nitrogen regulation (Ntr) system. We have investigated the role of this enzyme in transcriptional regulation of nitrogen fixation genes in Klebsiella pneumoniae by cloning glnD from this organism and constructing a null mutant by insertional inactivation of the chromosomal gene using the omega interposon. K. pneumoniae glnD encodes a 102.3 kDa polypeptide which is highly homologous to the predicted products of both Escherichia coli glnD and Azotobacter vinelandii nfrX. The glnD-omega mutant was unable to uridylylate PII and was altered in adenylylation/deadenylylation of glutamine synthetase. Uridylyltransferase was required for derepression of ntr-regulated promoters such as glnAp2 and pnifL but was not involved in the nif-specific response to changes in nitrogen status mediated by the nifL product. We conclude that a separate, as yet uncharacterised, nitrogen control system may be responsible for nitrogen sensing by NifL.
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Affiliation(s)
- R Edwards
- Nitrogen Fixation Laboratory, University of Sussex, Brighton, UK
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39
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Affiliation(s)
- M A Cleary
- Willink Biochemical Genetics Unit, Royal Manchester Children's Hospital, Pendlebury, UK
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40
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Elsas LJ, Dembure PP, Langley S, Paulk EM, Hjelm LN, Fridovich-Keil J. A common mutation associated with the Duarte galactosemia allele. Am J Hum Genet 1994; 54:1030-6. [PMID: 8198125 PMCID: PMC1918187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The human cDNA and gene for galactose-1-phosphate uridyl transferase (GALT) have been cloned and sequenced. A prevalent mutation (Q188R) is known to cause classic galactosemia (G/G). G/G galactosemia has an incidence of 1/38,886 in 1,396,766 Georgia live-born infants, but a more common variant of galactosemia, Duarte, has an unknown incidence. The proposed Duarte biochemical phenotypes of GALT are as follows: D/N, D/D, and D/G, which have approximately 75%, 50%, and 25% of normal GALT activity respectively. In addition, the D allele has isoforms of its enzyme that have more acidic pI than normal. Here we systematically determine (a) the prevalence of an A-to-G transition at base pair 2744 of exon 10 in the GALT gene, transition that produces a codon change converting asparagine to aspartic acid at position 314 (N314D), and (b) the association of this mutation with the Duarte biochemical phenotype. The 2744G nucleotide change adds an AvaII (SinI) cut site, which was identified in PCR-amplified DNA. In 111 biochemically unphenotyped controls with no history of galactosemia, 13 N314D alleles were identified (prevalence 5.9%). In a prospective study, 40 D alleles were biochemically phenotyped, and 40 N314D alleles were found. By contrast, in 36 individuals known not to have the Duarte biochemical phenotype, no N314D alleles were found. We conclude that the N314D mutation is a common allele that probably causes the Duarte GALT biochemical phenotype and occurs in a predominantly Caucasian, nongalactosemic population, with a prevalence of 5.9%.
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Affiliation(s)
- L J Elsas
- Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30322
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41
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van Heeswijk WC, Rabenberg M, Westerhoff HV, Kahn D. The genes of the glutamine synthetase adenylylation cascade are not regulated by nitrogen in Escherichia coli. Mol Microbiol 1993; 9:443-57. [PMID: 8412694 DOI: 10.1111/j.1365-2958.1993.tb01706.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Regulation of glutamine-synthetase (GS) activity in enteric bacteria involves a complex cascade of events. In response to nitrogen limitation, a transferase catalyses the uridylylation of the PII protein, which in turn stimulates deadenylylation of GS. Deadenylylated GS is the more active form of the enzyme. Here we characterize in detail the genes from Escherichia coli encoding uridylyl-transferase (glnD), the PII protein (glnB), and adenylyl-transferase (glnE). glnD is transcribed from its own promoter, glnE is contranscribed with another gene, orfXE, whereas glnB is partly contranscribed with a gene encoding a homologue of the transcription activator NtrC. All three gln regulatory genes were constitutively expressed at a low level, i.e. their expression was independent of the nitrogen status and the RNA polymerase sigma factor sigma 54. We conclude that the functioning of the GS adenylylation cascade is regulated by modulation of the activities of uridylyl-transferase and adenylyl-transferase, rather than by changes in the expression of their genes.
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Affiliation(s)
- W C van Heeswijk
- E. C. Slater Institute, University of Amsterdam, The Netherlands
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Schwacha A, Bender RA. The product of the Klebsiella aerogenes nac (nitrogen assimilation control) gene is sufficient for activation of the hut operons and repression of the gdh operon. J Bacteriol 1993; 175:2116-24. [PMID: 8458854 PMCID: PMC204320 DOI: 10.1128/jb.175.7.2116-2124.1993] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
In Klebsiella aerogenes, the formation of a large number of enzymes responds to the quality and quantity of the nitrogen source provided in the growth medium, and this regulation requires the action of the nitrogen regulatory (NTR) system in every case known. Nitrogen regulation of several operons requires not only the NTR system, but also NAC, the product of the nac gene, raising the question of whether the role of NAC is to activate operons directly or by modifying the specificity of the NTR system. We isolated an insertion of the transposon Tn5tac1 which puts nac gene expression under the control of the IPTG-inducible tac promoter rather than the nitrogen-responsive nac promoter. When IPTG was present, cells carrying the tac-nac fusion activated NAC-dependent operons and repressed NAC-repressible operons independent of the nitrogen supply and even in the absence of an active NTR system. Thus, NAC is sufficient to regulate operons like hut (encoding histidase) and gdh (encoding glutamate dehydrogenase), confirming the model that the NTR system activates nac expression and NAC activates hut and represses gdh. Activation of urease formation occurred at a lower level of NAC than that required for glutamate dehydrogenase repression, and activation of histidase formation required still more NAC.
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Affiliation(s)
- A Schwacha
- Department of Biology, University of Michigan, Ann Arbor 48109-1048
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van Heeswijk W, Kuppinger O, Merrick M, Kahn D. Localization of the glnD gene on a revised map of the 200-kilobase region of the Escherichia coli chromosome. J Bacteriol 1992; 174:1702-3. [PMID: 1537813 PMCID: PMC206572 DOI: 10.1128/jb.174.5.1702-1703.1992] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Affiliation(s)
- W van Heeswijk
- E.C. Slater Institute for Biochemical Research, University of Amsterdam, The Netherlands
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Contreras A, Drummond M, Bali A, Blanco G, Garcia E, Bush G, Kennedy C, Merrick M. The product of the nitrogen fixation regulatory gene nfrX of Azotobacter vinelandii is functionally and structurally homologous to the uridylyltransferase encoded by glnD in enteric bacteria. J Bacteriol 1991; 173:7741-9. [PMID: 1683868 PMCID: PMC212563 DOI: 10.1128/jb.173.24.7741-7749.1991] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We sequenced the nitrogen fixation regulatory gene nfrX from Azotobacter vinelandii, mutations in which cause a Nif- phenotype, and found that it encodes a 105-kDa protein (NfrX), the N terminus of which is highly homologous to that of the uridylyltransferase-uridylyl-removing enzyme encoded by glnD in Escherichia coli. In vivo complementation experiments demonstrate that the glnD and nfrX products are functionally interchangeable. A vinelandii nfrX thus appears to encode a uridylyltransferase-uridylyl-removing enzyme, and in this paper we report the first sequence of such a protein. The Nif- phenotype of nfrX mutants can be suppressed by a second mutation in a recently identified nifL-like gene immediately upstream of nifA in A. vinelandii. NifL mediates nif regulation in response to the N status in A. vinelandii, presumably by inhibiting NifA activator function as occurs in Klebsiella pneumoniae; thus, one role of NfrX is to modify, either directly or indirectly, the activity of the nifL product.
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Affiliation(s)
- A Contreras
- Agriculture and Food Research Council Nitrogen Fixation Laboratory, University of Sussex, Brighton, United Kingdom
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45
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Kim J, Ruzicka F, Frey PA. Remodeling hexose-1-phosphate uridylyltransferase: mechanism-inspired mutation into a new enzyme, UDP-hexose synthase. Biochemistry 1990; 29:10590-3. [PMID: 2271670 DOI: 10.1021/bi00499a003] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Hexose-1-phosphate uridylyltransferase catalyzes the interconversion of UDP-galactose and glucose-1-P with UDP-glucose and galactose-1-P by a double-displacement mechanism through a covalent intermediate (E-UMP), in which UMP is bonded to one of two histidine residues at the active site, H164 or H166. To identify which histidine is the nucleophilic catalyst, we prepared two specific mutants of the enzyme from Escherichia coli, H164G and H166G, in each of which the imidazole ring and methylene carbon of one histidine are deleted. To determine whether the function of the deleted imidazole in these mutants could be carried out by the imidazole ring in uridine 5'-(phosphoimidazolate) (UMP-Im), we examined the mutant proteins for catalytic activity in the reaction of UMP-Im with glucose-1-P to form UDP-glucose and imidazole. The mutant H166G catalyzes this reaction, as well as the reverse reaction, by a sequential kinetic mechanism involving ternary complexes as intermediates. The mutant enzyme also accepts galactose-1-P as a substrate to form UDP-galactose. Hexose-1-P uridylyltransferase does not catalyze these reactions, and H166G does not catalyze the wild-type reaction. The substrate Km values for the mutant enzyme are similar to those for hexose-1-P uridylyltransferase. The value of kcat in the direction of UDP-glucose formation is 1.31 +/- 0.01 s-1, compared with 350 s-1 for hexose-1-P uridylyltransferase, and in the reverse direction kcat is 4.8 +/- 0.4 s-1, compared with 960 s-1 for the wild-type enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J Kim
- Institute for Enzyme Research, College of Agricultural and Life Sciences, University of Wisconsin-Madison 53705
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46
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Abstract
To study the genetic expression and regulation of galactose-metabolizing enzymes, we mutagenized the mouse liver H2.35 cell line and selected for cell clones resistant to the toxic galactose analog, 2-deoxy-D-galactose (2-DOG). One cloned line, designated H12.10, was stably resistant to high levels of 2-DOG and was completely deficient in galactokinase activity. Galactokinase activity and growth sensitivity to 2-DOG could be restored by transfecting H12.10 cells with a plasmid containing the Escherichia coli galactokinase (galK) gene fused to a eucaryotic promoter; thus, the 2-DOG selection could be directed against transfected recombinant constructs in a liver cell line. We also found that H2.35 cells could not utilize galactose as a primary carbon source because of a deficiency in galactose-1-phosphate uridyltransferase; a variant line of H2.35 cells selected in galactose medium expressed higher levels of uridyltransferase activity. Finally, we found that in all mammalian cell lines tested, galactokinase expression was the same whether the medium contained glucose, galactose, or both sugars. These studies demonstrate differences between mammalian cells and yeast cells in the regulation of gal enzymes, and they define different schemes for obtaining altered expression of genes in the galactose metabolic pathway. The isogenic liver cell lines described here can also serve as model systems for studying galactosemias, which are inherited disorders of galactose metabolism in humans.
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Affiliation(s)
- K S Zaret
- Section of Biochemistry, Brown University, Providence, Rhode Island 02912
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Affiliation(s)
- L Simpson
- Department of Biology, University of California, Los Angeles 90024
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Scherz R, Breguet G, Ney R, Pflugshaupt R, Bütler R. Study of five haemogenetic markers (Gc, C3, Bf, Ag, and GALT) in six Indonesian populations and in 12 subgroups of Balinese. Am J Phys Anthropol 1988; 76:489-96. [PMID: 2851268 DOI: 10.1002/ajpa.1330760408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In various ethnic groups of the Indonesian archipelago and of Bali, the polymorphisms of the serum proteins Gc globulin (vitamin D-binding protein), C3 (complement component 3), Bf (complement factor B), Ag x,y (lipoprotein allotypes), and of the red cell enzyme system GALT (galactose-1P-uridyltransferase) were analysed. Among the studied proteins, the Gc system was the most informative one for the anthropologist. Besides considerable differences of frequencies of the common alleles Gc*1F, Gc*1S and Gc*2, a number of rare alleles (1A1, 1A3, 1A8, 1A9, 1A12, 1C2, 1C21, 1C24, and 2C8) and some new ones (1C28, 1C29, 1C30, 2C9) were observed. The presence of Gc*1A1 demonstrates the relationship to the Australo-Melanesian populations, but Mongolian variants (1A3, 1A8, 1A9, 1C2) were also encountered. Within the C3 system a very high frequency of the C3*S allele was observed in all populations. The rare alleles C3*F0.55, C3S1, and C3*S0.5 were observed in some groups. A new allele (C3*F0.35) was detected in a Chinese individual and in a nobleman from Bali. The frequency of the Bf*F allele was rather low in general, and the Bf*S0.7 allele was found in three Indonesian individuals only. The Ag*(x) frequencies were rather high, as it is known for Asiatic populations. Variability among subgroups was not very pronounced. The GALT*2 allele (Duarte variant of the enzyme) was observed very rarely; however, it was present in several populations. Enzyme activities could not be determined, and therefore we cannot tell whether the galactosaemia gene (GALT*0) was present or not.
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Affiliation(s)
- R Scherz
- Central Laboratory, Blood Transfusion Service, Bern, Switzerland
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Affiliation(s)
- T L Cornwell
- Institute for Enzyme Research, Graduate School, University of Wisconsin, Madison
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