1
|
Coelho AI, Rubio-Gozalbo ME, Vicente JB, Rivera I. Sweet and sour: an update on classic galactosemia. J Inherit Metab Dis 2017; 40:325-342. [PMID: 28281081 PMCID: PMC5391384 DOI: 10.1007/s10545-017-0029-3] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 02/14/2017] [Accepted: 02/20/2017] [Indexed: 02/03/2023]
Abstract
Classic galactosemia is a rare inherited disorder of galactose metabolism caused by deficient activity of galactose-1-phosphate uridylyltransferase (GALT), the second enzyme of the Leloir pathway. It presents in the newborn period as a life-threatening disease, whose clinical picture can be resolved by a galactose-restricted diet. The dietary treatment proves, however, insufficient in preventing severe long-term complications, such as cognitive, social and reproductive impairments. Classic galactosemia represents a heavy burden on patients' and their families' lives. After its first description in 1908 and despite intense research in the past century, the exact pathogenic mechanisms underlying galactosemia are still not fully understood. Recently, new important insights on molecular and cellular aspects of galactosemia have been gained, and should open new avenues for the development of novel therapeutic strategies. Moreover, an international galactosemia network has been established, which shall act as a platform for expertise and research in galactosemia. Herein are reviewed some of the latest developments in clinical practice and research findings on classic galactosemia, an enigmatic disorder with many unanswered questions warranting dedicated research.
Collapse
Affiliation(s)
- Ana I Coelho
- Department of Pediatrics and Department of Clinical Genetics, Maastricht University Medical Centre, P. Debyelaan 25, PO Box 5800, 6202 AZ, Maastricht, The Netherlands.
| | - M Estela Rubio-Gozalbo
- Department of Pediatrics and Department of Clinical Genetics, Maastricht University Medical Centre, P. Debyelaan 25, PO Box 5800, 6202 AZ, Maastricht, The Netherlands
| | - João B Vicente
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Isabel Rivera
- Metabolism & Genetics Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal
- Department of Biochemistry and Human Biology, Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal
| |
Collapse
|
2
|
McCorvie TJ, Timson DJ. The structural and molecular biology of type I galactosemia: Enzymology of galactose 1-phosphate uridylyltransferase. IUBMB Life 2011; 63:694-700. [PMID: 21793161 DOI: 10.1002/iub.511] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Accepted: 05/06/2011] [Indexed: 11/10/2022]
Abstract
Reduced galactose 1-phosphate uridylyltransferase (GALT) activity is associated with the genetic disease type I galactosemia. This results in an increase in the cellular concentration of galactose 1-phosphate. The accumulation of this toxic metabolite, combined with aberrant glycoprotein and glycolipid biosynthesis, is likely to be the major factor in molecular pathology. The mechanism of GALT was established through classical enzymological methods to be a substituted enzyme in which the reaction with UDP-glucose results in the formation of a covalent, UMP-histidine adduct in the active site. The uridylated enzyme can then react with galactose 1-phosphate to form UDP-galactose. The structure of the enzyme from Escherichia coli reveals a homodimer containing one zinc (II) and one iron (II) ion per subunit. This enzymological and structural knowledge provides the basis for understanding the biochemistry of this critical step in the Leloir pathway. However, a high-resolution crystal structure of human GALT is required to assist greater understanding of the effects of disease-associated mutations.
Collapse
Affiliation(s)
- Thomas J McCorvie
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, Belfast, BT9 7BL, UK
| | | |
Collapse
|
3
|
Frey PA. Sulfur as a mechanistic probe in enzymatic and non-enzymatic substitution at phosphorus. NEW J CHEM 2010. [DOI: 10.1039/b9nj00619b] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
4
|
Juodka BA. Covalent Interaction of Proteins and Nucleic Acids. Synthetic and Natural Nucleotide-Peptides. ACTA ACUST UNITED AC 2007. [DOI: 10.1080/07328318408081283] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
5
|
Frey PA. Chiral phosphorothioates: stereochemical analysis of enzymatic substitution at phosphorus. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 62:119-201. [PMID: 2658487 DOI: 10.1002/9780470123089.ch4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- P A Frey
- Institute for Enzyme Research, Graduate School, College of Agricultural and Life Sciences, University of Wisconsin, Madison 53705
| |
Collapse
|
6
|
Huang K, Arabshahi A, Frey PA. pH-Dependence in the Hydrolytic Action of the Human Fragile Histidine Triad. European J Org Chem 2005. [DOI: 10.1002/ejoc.200500499] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
7
|
Geeganage S, Frey PA. Galactose-1-phosphate uridylyltransferase: kinetics of formation and reaction of uridylyl-enzyme intermediate in wild-type and specifically mutated uridylyltransferases. Methods Enzymol 2003; 354:134-48. [PMID: 12418221 DOI: 10.1016/s0076-6879(02)54010-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/27/2023]
Affiliation(s)
- Sandaruwan Geeganage
- Cancer Research Division, Eli Lilly and Company, Indianapolis, Indiana 46285, USA
| | | |
Collapse
|
8
|
Henderson JM, Wells L, Fridovich-Keil JL. Covalent heterogeneity of the human enzyme galactose-1-phosphate uridylyltransferase. J Biol Chem 2000; 275:30088-91. [PMID: 10884393 DOI: 10.1074/jbc.m005259200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Galactose-1-phosphate uridylyltransferase (GALT) acts by a double displacement mechanism, catalyzing the second step in the Leloir pathway of galactose metabolism. Impairment of this enzyme results in the potentially lethal disorder, galactosemia. Although the microheterogeneity of native human GALT has long been recognized, the biochemical basis for this heterogeneity has remained obscure. We have explored the possibility of covalent GALT heterogeneity using denaturing two-dimensional gel electrophoresis and Western blot analysis to fractionate and visualize hemolysate hGALT, as well as the human enzyme expressed in yeast. In both contexts, two predominant GALT species were observed. To define the contribution of uridylylated enzyme intermediate to the two-spot pattern, we exploited the null allele, H186G-hGALT. The Escherichia coli counterpart of this mutant protein (H166G-eGALT) has previously been demonstrated to fold properly, although it cannot form covalent intermediate. Analysis of the H186G-hGALT protein demonstrated a single predominant species, implicating covalent intermediate as the basis for the second spot in the wild-type pattern. In contrast, three naturally occurring mutations, N314D, Q188R, and S135L-hGALT, all demonstrated the two-spot pattern. Together, these data suggest that uridylylated hGALT comprises a significant fraction of the total GALT enzyme pool in normal human cells and that three of the most common patient mutations do not disrupt this distribution.
Collapse
Affiliation(s)
- J M Henderson
- Graduate Program in Nutrition and Health Sciences, the Graduate Program in Biochemistry and Molecular Biology, and the Department of Genetics, Emory University School of Medicine, Atlanta, Georgia 30322, USA
| | | | | |
Collapse
|
9
|
Lai K, Willis AC, Elsas LJ. The biochemical role of glutamine 188 in human galactose-1-phosphate uridyltransferase. J Biol Chem 1999; 274:6559-66. [PMID: 10037750 DOI: 10.1074/jbc.274.10.6559] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The substitution of arginine for glutamine at amino acid 188 (Q188R) ablates the function of human galactose-1-phosphate uridyltransferase (GALT) and is the most common mutation causing galactosemia in the white population. GALT catalyzes two consecutive reactions. The first reaction binds UDP-glucose (UDP-Glu), displaces glucose-1-phosphate (glu-1-P), and forms the UMP-GALT intermediate. In the second reaction, galactose-1-phosphate (gal-1-P) is bound, UDP-galactose (UDP-Gal) is released, and the free enzyme is recycled. In this study, we modeled glutamine, asparagine, and a common mutation arginine at amino acid 188 on the three-dimensional model of the Escherichia coli GALT-UMP protein crystal. We found that the amide group of the glutamine side chain could provide two hydrogen bonds to the phosphoryl oxygens of UMP with lengths of 2.52 and 2.82 A. Arginine and asparagine could provide only one hydrogen bond of 2. 52 and 3.02 A, respectively. To test this model, we purified recombinant human Gln188-, Arg188-, and Asn188-GALT and analyzed the first reaction in the absence of gal-1-P by quantitating glu-1-P released using enzyme-linked methods. Gln188-GALT displaced 80 +/- 7. 0 nmol glu-1-P/mg GALT/min in the first reaction. By contrast, both Arg188- and Asn188-GALT released more glu-1-P (170 +/- 8.0 and 129 +/- 28.4 nmol/mg GALT/min, respectively). The overall, double displacement reaction was quantitated in the presence of gal-1-P. Gln188-GALT produced 80,030 +/- 5,910 nmol glu-1-P/mg GALT/min, whereas the mutant Arg188- and Asn188-GALT released only 600 +/- 71. 2 and 2960 +/- 283.6 nmole glu-1-P/mg GALT/min, respectively. We conclude from these data that glutamine at position 188 stabilizes the UMP-GALT intermediate through hydrogen bonding and enables the double displacement of both glu-1-P and UDP-Gal. The substitution of arginine or asparagine at position 188 reduces hydrogen bonding and destabilizes UMP-GALT. The unstable UMP-GALT allows single displacement of glu-1-P with release of free GALT but impairs the subsequent binding of gal-1-P and displacement of UDP-Gal.
Collapse
Affiliation(s)
- K Lai
- Division of Medical Genetics, Departments of Biochemistry and Pediatrics, Emory University School of Medicine, Atlanta, Georgia 30322, USA
| | | | | |
Collapse
|
10
|
Abstract
Classic galactosemia is an autosomal recessive disorder caused by the deficiency of galactose 1-phosphate uridyltransferase (GALT). Although the potentially lethal, neonatal hepatotoxic syndrome is prevented by newborn screening and galactose restriction, long-term outcome for older patients with galactosemia remains problematic. After the cloning and sequencing of the GALT gene, more than 130 mutations in the GALT gene have been associated with GALT deficiency; this review relates them to function and clinical outcome. Two common mutations, Q188R and K285N, account for more than 70% of G alleles in the white population and are associated with classic galactosemia and impaired GALT function. In the black population, S135L accounts for 62% of the alleles causing galactosemia and is associated with good outcomes. A large 5 kb deletion in the GALT gene is found in Ashkenazim Jews. The Duarte galactosemia variant is caused by N314D. Homozygosity for N314D reduces GALT activity to 50%. When either E203K or a 1721C-->T transition (Los Angeles variant) are present in cis with N314D, GALT activity reverts to normal. In this review, we discuss the structural biology of these mutations as they affect both the GALT enzyme and patient outcome.
Collapse
Affiliation(s)
- L J Elsas
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
| | | |
Collapse
|
11
|
Wells L, Fridovich-Keil JL. Biochemical characterization of the S135L allele of galactose-1-phosphate uridylyltransferase associated with galactosaemia. J Inherit Metab Dis 1997; 20:633-42. [PMID: 9323558 DOI: 10.1023/a:1005314207513] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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.
Collapse
Affiliation(s)
- L Wells
- Graduate Program in Biochemistry and Molecular Biology, Emory University School of Medicine, Atlanta, Georgia, USA
| | | |
Collapse
|
12
|
Elsevier JP, Fridovich-Keil JL. The Q188R mutation in human galactose-1-phosphate uridylyltransferase acts as a partial dominant negative. J Biol Chem 1996; 271:32002-7. [PMID: 8943248 DOI: 10.1074/jbc.271.50.32002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
A longstanding goal in the fields of molecular genetics and biochemistry has been to explain how naturally occurring mutations associated with human metabolic disease impair activity of the enzymes involved. This goal is particularly complex for enzymes composed of multiple subunits, because single mutations may exert both intra- and intersubunit effects on holoenzyme structure and function. We have previously applied a yeast coexpression system for human galactose-1-phosphate uridylyltransferase, a dimeric enzyme associated with galactosemia, to investigate the impact of naturally occurring mutations on subunit association and holoenzyme function (). Here we describe the purification and characterization of two heterodimers, R333W/wild type (WT) and Q188R/WT, revealing that although the first exhibits approximately 50% wild-type activity, the second exhibits only approximately 15% wild-type activity. Neither heterodimer varied significantly from the wild type with regard to apparent Km for either substrate, although Q188R/WT but not R333W/WT heterodimers demonstrated significantly increased thermal sensitivity relative to the wild-type enzyme. These results demonstrate for the first time a partial dominant negative effect caused by a naturally occurring mutation in human galactose-1-phosphate uridylyltransferase.
Collapse
Affiliation(s)
- J P Elsevier
- Graduate Program in Biochemistry and Molecular Biology, Emory University, Atlanta, Georgia 30322, USA
| | | |
Collapse
|
13
|
Quimby BB, Wells L, Wilkinson KD, Fridovich-Keil JL. Functional requirements of the active site position 185 in the human enzyme galactose-1-phosphate uridylyltransferase. J Biol Chem 1996; 271:26835-42. [PMID: 8900165 DOI: 10.1074/jbc.271.43.26835] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The active site of galactose-1-phosphate uridylyltransferase (GALT) includes a HPH sequence that has been conserved in all species examined from Escherichia coli to humans. The crystal structure of the E. coli enzyme suggests that this proline is important in positioning the active site histidine (His-166) near the substrate. To examine the role of this proline in the homologous human sequence, we have performed saturating mutagenesis at Pro-185 within human GALT and characterized each resultant mutant enzyme using a yeast expression system. Activity analyses in crude lysates indicated that only proline at position 185 produced wild-type levels of activity, although five other amino acids, Ala, Gly, Ser, Gln, and Glu, all produced partially active enzymes. Western blot analyses of the GALT proteins in these lysates demonstrated that abundance varied from 9-118% of wild-type and was independent of activity. All five active mutant proteins were purified and characterized with regard to specific activity, apparent Km for both substrates, and temperature-dependence of activity. Finally, modeling of these mutations onto the conserved E. coli active site structure was performed. Together, these results provide functional evidence demonstrating the critical role of Pro-185 in facilitating the transferase reaction.
Collapse
Affiliation(s)
- B B Quimby
- Graduate Program in Genetics and Molecular Biology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
| | | | | | | |
Collapse
|
14
|
O'Toole GA, Escalante-Semerena JC. Purification and characterization of the bifunctional CobU enzyme of Salmonella typhimurium LT2. Evidence for a CobU-GMP intermediate. J Biol Chem 1995; 270:23560-9. [PMID: 7559521 DOI: 10.1074/jbc.270.40.23560] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The CobU protein of Salmonella typhimurium was overexpressed and purified to approximately 94% homogeneity. N-terminal sequencing of purified CobU confirmed the first 22 amino acids. In vitro assays showed that CobU has kinase and guanylyltransferase activities which catalyze the synthesis of adenosyl-cobinamide-GDP from adenosyl-cobinamide, via an adenosyl-cobinamide-phosphate intermediate. We present evidence that the transfer of the guanylyl moiety of GTP to adenosyl-cobinamide-phosphate proceeds via an phosphoramidate-linked, enzyme-guanylyl intermediate. In the presence of oxygen, kinase and guanylyltransferase activities of CobU were lost. Treatment of inactive CobU with dithiothreitol restored approximately 20% of the kinase and guanylyltransferase activities, indicating the involvement of sulfhydryl groups in enzyme activity. The sulfhydryl modifying agents 5,5'-dithiobis(2-nitrobenzoic acid) and N-ethylmaleimide abolished both CobU activities. Native CobU protein was a dimer (approximately 40 kDa) that functioned optimally at pH 8.8-9.0 and 37 degrees C. Substrates and kinetic parameters for both activities were determined. The preferred corrinoid substrate for this enzyme was adenosyl-cobinamide. In vitro experiments are consistent with previous genetic studies which had suggested that adenosyl-cobinamide was the preferred substrate of CobU, and that CobU functioned more efficiently in the absence of oxygen.
Collapse
Affiliation(s)
- G A O'Toole
- Department of Bacteriology, University of Wisconsin, Madison 53706, USA
| | | |
Collapse
|
15
|
Wedekind JE, Frey PA, Rayment I. Three-dimensional structure of galactose-1-phosphate uridylyltransferase from Escherichia coli at 1.8 A resolution. Biochemistry 1995; 34:11049-61. [PMID: 7669762 DOI: 10.1021/bi00035a010] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Galactose-1-phosphate uridylyltransferase catalyzes the reversible transfer of the uridine 5'-monophosphoryl moiety of UDP-glucose to the phosphate group of galactose 1-phosphate to form UDP-galactose. This enzyme participates in the Leloir pathway of galactose metabolism, and its absence is the primary cause of the potentially lethal disease galactosemia. The three-dimensional structure of the dimeric enzyme from Escherichia coli complexed with uridine 5'-diphosphate is reported here. The structure was solved by multiple isomorphous replacement and electron density modification techniques and has been refined to 1.8 A resolution. Enzyme subunits consist of a single domain with the topology of a "half-barrel". The barrel staves are formed by nine strands of antiparallel beta-sheet. The barrel axis is approximately parallel to the local dyad that relates each subunit. Two amphipathic helices fill the half-barrel sequestering its hydrophobic interior. An iron atom resides on the outside of the barrel, centered in the subunit interface. Intrasubunit coordination to iron resembles a distorted square pyramid formed by the equatorial ligation of two histidines and a bidentate carboxylate group and a single axial histidine. The subunit interface is stabilized by this coordination and is further characterized by the formation of two intermolecular "mini-sheets" distinct from the strands of the half-barrel. Loops that connect the mini-sheet strands contribute to the formation of the active site, which resides on the external surface of the barrel rim. Loops of the barrel strands are tethered together by a structural zinc atom that orients the local fold in a manner essential for catalysis. In one of the latter loops, S gamma of a cysteine is modified by beta-mercaptoethanol, which prevents the alpha-phosphorus of the nucleotide from access to the nucleophile His166. This conformation does not appear to perturb the interactions to the uracil and ribose moieties as mediated through the side chains of Leu54, Ohe75, Asn77, Asp78, Phe79, and Val108. Several of the latter residues have been implicated in human galactosemia. The present structure explains the deleterious effects of many of those mutations.
Collapse
Affiliation(s)
- J E Wedekind
- Institute for Enzyme Research, Graduate School, University of Wisconsin-Madison 53705, USA
| | | | | |
Collapse
|
16
|
Vorgias CE, Lemaire HG, Wilson KS. Overexpression and purification of the galactose operon enzymes from Escherichia coli. Protein Expr Purif 1991; 2:330-8. [PMID: 1821806 DOI: 10.1016/1046-5928(91)90091-v] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A convenient new procedure for the purification of galactokinase, galactose-1-phosphate uridyltransferase, and UDP-galactose 4-epimerase overexpressed in Escherichia coli is presented. The procedure is shorter than any other described in the literature and facilitates the purification of the three recombinant enzymes in considerable amounts and at high purity and specific activity. The purified gal operon enzymes were biochemically characterized by gel-filtration column chromatography and isoelectric focusing, and the Km values for their substrates were determined.
Collapse
Affiliation(s)
- C E Vorgias
- European Molecular Biology Laboratory, c/o DESY, Hamburg, Germany
| | | | | |
Collapse
|
17
|
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] [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)
Collapse
Affiliation(s)
- J Kim
- Institute for Enzyme Research, College of Agricultural and Life Sciences, University of Wisconsin-Madison 53705
| | | | | |
Collapse
|
18
|
Williams VP, Helmer GR, Fried C. Human galactose-1-phosphate uridylyltrsferase: purification and comparison of the red blood cell and placental enzymes. Arch Biochem Biophys 1982; 216:503-11. [PMID: 6287937 DOI: 10.1016/0003-9861(82)90239-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
|
19
|
Frey PA, Wong LJ, Sheu KF, Yang SL. Galactose-1-phosphate uridylyltransferase: detection, isolation, and characterization of the uridylyl enzyme. Methods Enzymol 1982; 87:20-36. [PMID: 6294449 DOI: 10.1016/s0076-6879(82)87004-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
|
20
|
|
21
|
|
22
|
Frey PA. Chapter 5 Stereochemistry of enzymatic substitution at phosphorus. ACTA ACUST UNITED AC 1982. [DOI: 10.1016/s0167-7306(08)60396-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2023]
|
23
|
Williams VP, Fried C, Popják G. Human red cell galactose 1-phosphate uridylyltransferase: effects of site-specific reagents on catalytic activity. Arch Biochem Biophys 1981; 206:353-61. [PMID: 6261696 DOI: 10.1016/0003-9861(81)90102-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
|
24
|
Sheu KF, Richard JP, Frey PA. Stereochemical courses of nucleotidyltransferase and phosphotransferase action. Uridine diphosphate glucose pyrophosphorylase, galactose-1-phosphate uridylyltransferase, adenylate kinase, and nucleoside diphosphate kinase. Biochemistry 1979; 18:5548-56. [PMID: 229894 DOI: 10.1021/bi00592a004] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
25
|
Yang SL, Frey PA. Nucleophile in the active site of Escherichia coli galactose-1-phosphate uridylyltransferase: degradation of the uridylyl-enzyme intermediate to N3-phosphohistidine. Biochemistry 1979; 18:2980-4. [PMID: 380639 DOI: 10.1021/bi00581a011] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The [32P]uridylyl-enzyme intermediate form of Escherichia coli galactose-1-P uridylyltransferase can be converted to a [32P]phosphoryl-enzyme by first cleaving the ribosyl ring with NaIO4 and then heating at pH 10.5 and 50 degrees C for 1 h. After alkaline hydrolysis of the [32P]phosphoryl-enzyme the major radioactive product is N3-[32P]phosphohistidine. A lesser amount of 32Pi is also produced as a side product of the hydrolysis of N3-[32P]phosphohistidine. No N1-phosphohistidine, N-phospholysine, or phosphoarginine can be detected in these hydrolysates. It is concluded that the nucleophile in galactose-1-P uridylyltransferase to which the uridylyl group is bonded in the uridylyl-enzyme intermediate is imidazole N3 of a histidine residue. This degradation procedure should have general applicability in the degradation and characterization of nucleotidyl-proteins.
Collapse
|
26
|
Williams VP. Purification and some properties of galactose 1-phosphate uridylyltransferase from human red cells. Arch Biochem Biophys 1978; 191:182-91. [PMID: 736561 DOI: 10.1016/0003-9861(78)90080-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
|
27
|
UDP-glucose pyrophosphorylase. Stereochemical course of the reaction of glucose 1-phosphate with uridine-5'[1-thiotriphosphate]. J Biol Chem 1978. [DOI: 10.1016/s0021-9258(17)34808-1] [Citation(s) in RCA: 43] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
|
28
|
Markus HB, Wu JW, Boches FS, Tedesco TA, Mellman WJ, Kallen RG. Human erythrocyte galactose-1-phosphate uridylyltransferase. Evidence for a uridylyl-enzyme intermediate by kinetic and exchange reaction studies. J Biol Chem 1977. [DOI: 10.1016/s0021-9258(19)63356-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
29
|
Mayes JS. Purification, properties, and isozyme pattern of galactose-1-phosphate uridyl transferase from calf liver. Arch Biochem Biophys 1976; 172:715-20. [PMID: 1259429 DOI: 10.1016/0003-9861(76)90128-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
|
30
|
|