201
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Chang SI, Kang MK, Choi JD, Namgoong SK. Soluble overexpression in Escherichia coli, and purification and characterization of wild-type recombinant tobacco acetolactate synthase. Biochem Biophys Res Commun 1997; 234:549-53. [PMID: 9175749 DOI: 10.1006/bbrc.1997.6678] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Acetolactate synthase (ALS) is the first common enzyme in the biosynthesis of L-leucine, L-isoleucine, and L-valine. The wild-type ALS gene from Nicotiana tabacum was cloned into the bacterial expression vector pGEX-2T. The resulting recombinant plasmid pGEX-ALS2 was used to transform Escherichia coli strain XL1-Blue, and the wild-type tobacco ALS (wALS) was expressed in the bacteria as a protein fused with glutathione S-transferase (GST). The fusion product GST-wALS was purified in a single step on a glutathione-Sepharose column. The purified GST-wALS was sensitive to a sulfonylurea herbicide, and was lost its sensitivity to end products, L-valine, L-leucine and L-isoleucine. These results suggest that the purified recombinant tobacco ALS was functionally active, and that the sulfonylureas may not bind to the feedback regulatory site on the plant ALS.
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Affiliation(s)
- S I Chang
- Department of Biochemistry, Chungbuk National University, Cheongju, Korea.
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202
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Dumas R, Biou V, Douce R. Purification and characterization of a fusion protein of plant acetohydroxy acid synthase and acetohydroxy acid isomeroreductase. FEBS Lett 1997; 408:156-60. [PMID: 9187358 DOI: 10.1016/s0014-5793(97)00410-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The nucleotide sequence coding for the Arabidopsis thaliana acetohydroxy acid synthase was genetically fused in frame with the nucleotide sequence coding for the Spinacia oleracea acetohydroxy acid isomeroreductase and expressed in Escherichia coli. This construction allowed the production of large amounts of soluble fusion protein. The pure chimeric enzyme exhibits high acetohydroxy acid synthase and acetohydroxy acid isomeroreductase specific activities. Fusion and native enzymes exhibit similar Km values for their substrates and for most cofactors. Furthermore, whereas native plant acetohydroxy acid synthase is highly unstable, the stability of this enzyme in the fusion has been increased. Thus, the chimeric enzyme appears to be a useful tool for the determination of kinetic and structural properties of plant acetohydroxy acid synthase.
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Affiliation(s)
- R Dumas
- Unité Mixte CNRS/Rhône-Poulenc Agrochimie (UMR 41), Lyon, France
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203
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Coakley M, Fitzgerald G, Ros RP. Application and evaluation of the phage resistance- and bacteriocin-encoding plasmid pMRC01 for the improvement of dairy starter cultures. Appl Environ Microbiol 1997; 63:1434-40. [PMID: 9097441 PMCID: PMC168438 DOI: 10.1128/aem.63.4.1434-1440.1997] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The conjugative 63-kb lactococcal plasmid pMRC01 encodes bacteriophage resistance and production of and immunity to a novel broad-spectrum bacteriocin, designated lacticin 3147 (M.P. Ryan, M.C. Rea, C. Hill, and R.P. Ross, Appl. Environ. Microbiol. 62:612-619, 1996). The phage resistance is an abortive infection mechanism which targets the phage-lytic cycle at a point after phage DNA replication. By using the genetic determinants for bacteriocin immunity encoded on the plasmid as a selectable marker, pMRC01 was transferred into a variety of lactococcal starter cultures to improve their phage resistance properties. Selection of resulting transconjugants was performed directly on solid media containing the bacteriocin. Since the starters exhibited no spontaneous resistance to the bacteriocin as a selective agent, this allowed the assessment of the transfer of the naturally occurring plasmid into a range of dairy starter cultures. Results demonstrate that efficient transfer of the plasmid was dependent on the particular recipient strain chosen, and while high-frequency transfer (10(-3) per donor) of the entire plasmid to some strains was observed, the plasmid could not be conjugated into a number of starters. In this study, transconjugants for a number of lactococcal starter cultures which are phage resistant and bacteriocin producing have been generated. This bacteriocin-producing phenotype allows for control of nonstarter flora in food fermentations, and the phage resistance property protects the starter cultures in industry. The 63-kb plasmid was also successfully transferred into Lactococcus lactis MG1614 cells via electroporation.
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Affiliation(s)
- M Coakley
- National Dairy Products Research Centre, Fermoy, County Cork, Ireland
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204
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Morbach S, Sahm H, Eggeling L. l-Isoleucine Production with Corynebacterium glutamicum: Further Flux Increase and Limitation of Export. Appl Environ Microbiol 1996; 62:4345-51. [PMID: 16535457 PMCID: PMC1388995 DOI: 10.1128/aem.62.12.4345-4351.1996] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The synthesis of l-isoleucine with Corynebacterium glutamicum involves 11 reaction steps, in at least five of which activity or expression is regulated. We used four genes and alleles encoding feedback-resistant enzymes (Fbr) in various combinations to assay flux increase through the sequence. During strain construction, the order of genes overexpressed was important. Only when ilvA(Fbr) was first overexpressed could hom(Fbr) be introduced. This succession apparently prevents the toxic accumulation of biosynthesis intermediates. The best strain constructed (SM13) was characterized by high-level expression of hom(Fbr), thrB, and ilvA(Fbr). With this strain a yield of 0.22 g of l-isoleucine per g of glucose was obtained, with a maximal specific productivity of 0.10 g of l-isoleucine per g (dry weight) per h. In strain SM13, with the high metabolite flux through the reaction sequence, effects on (i) other enzyme levels, (ii) time-dependent variations with process time, and (iii) concentrations of cytosolic intermediates were quantified. Most importantly, the intracellular l-isoleucine concentration is always higher at all process times than the extracellular concentration. The intracellular concentration rises to 110 mM, whereas extracellularly only 60 mM is accumulated. Also the immediate l-isoleucine precursor 2-ketomethyl valerate accumulates in the cell. Therefore, in the high-level l-isoleucine producer SM13, the export of this amino acid is the major limiting reaction step and therefore is a new target of strain design for biotechnological purposes.
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205
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Cullin C, Baudin-Baillieu A, Guillemet E, Ozier-Kalogeropoulos O. Functional analysis of YCL09C: evidence for a role as the regulatory subunit of acetolactate synthase. Yeast 1996; 12:1511-8. [PMID: 8972574 DOI: 10.1002/(sici)1097-0061(199612)12:15<1511::aid-yea41>3.0.co;2-b] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We have analysed the function of the open reading frame (ORF) YCL09C. The deletion of this ORF from chromosome III does not affect the physiology of the corresponding yeast strain enough to give a distinct phenotype. Nevertheless a computational analysis reveals high homology between this ORF and the enterobacterial genes encoding the regulatory subunit of acetolactate synthase. We have therefore tested the possibility that yc109cp is the regulatory subunit of yeast acetolactate synthase by in vitro enzymatic analysis. The acetolactate synthase was previously shown to be retroinhibited by its final product valine. In Escherichia coli this retro-control is assured by the regulatory subunit. Using a yeast strain carrying a complete deletion of YCL09C, we have observed the loss of such retro-inhibition. These results together with the computational predictions show that YCL09C encodes the regulatory subunit of yeast acetolactate synthase.
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Affiliation(s)
- C Cullin
- Centre de Génétique Moléculaire du CNRS, Laboratoire Propre Associé à l'Université Pierre et Marie Curie, Gif-sur-Yvette, France
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206
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Jordan KN, O'donoghue M, Condon S, Cogan TM. Formation of diacetyl by cell-free extracts of Leuconostoc lactis. FEMS Microbiol Lett 1996. [DOI: 10.1111/j.1574-6968.1996.tb08495.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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207
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Vyazmensky M, Sella C, Barak Z, Chipman DM. Isolation and characterization of subunits of acetohydroxy acid synthase isozyme III and reconstitution of the holoenzyme. Biochemistry 1996; 35:10339-46. [PMID: 8756689 DOI: 10.1021/bi9605604] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The separately cloned large and small subunits of AHAS isozyme III from Escherichia coli have been isolated and purified. The essentially pure small subunit (17 kDa ilvH product) was obtained by a procedure exploiting its low solubility. The large, catalytic subunit (62 kDa ilvI product) was isolated by standard techniques, to > or = 95% purity. The large subunit has low catalytic activity relative to holoenzyme (approximately 5%) but shows similar substrate specificity and qualitatively similar cofactor dependence and inhibition by a sulfonylurea herbicide. Its activity is insensitive to valine, and the protein does not bind valine. The small subunit binds valine with Kd = 0.2 mM. Reconstitution of the holoenzyme from its subunits leads to a complex with the properties of the native protein, including valine inhibition of activity with Ki = 12 microM. Reconstitution titrations confirm the 1:1 stoichiometry of subunit assembly and a tendency to dissociation (about 50% dissociation near 0.1 microM subunit). Size exclusion HPLC indicates that either subunit alone is largely monomeric, and that assembly of the holoenzyme (two large + two small subunits, 150-160 kDa) requires FAD. On the basis of its homology with pyruvate oxidase and pyruvate decarboxylase, we suggest that the active sites of AHAS III are located at the interface of a dimer of catalytic subunits. Our experiments suggest that such a dimer is not stable except in the presence of the small subunits. The association of valine with sites on the regulatory subunits presumably influences the active sites by an allosteric conformational effect.
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Affiliation(s)
- M Vyazmensky
- Department of Life Science, Ben-Gurion University of the Negev, Israel
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208
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Dassy B, Fournier JM. Respiratory activity is essential for post-exponential-phase production of type 5 capsular polysaccharide by Staphylococcus aureus. Infect Immun 1996; 64:2408-14. [PMID: 8698459 PMCID: PMC174090 DOI: 10.1128/iai.64.7.2408-2414.1996] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Capsule formation is believed to have a significant role in bacterial virulence. To examine the possible involvement of capsular polysaccharide (CP) from Staphylococcus aureus in the pathological mechanisms associated with staphylococcal infections, we investigated the influence of respiratory activity on type 5 CP production by S. aureus grown in the presence of various concentrations of dissolved oxygen or nitrate. The effects of several metabolic inhibitors (arsenite, cyanide, azide, trimethylamine N-oxide, 2-heptyl-4-hydroxyquinoline N-oxide, and 2,4-dinitrophenol) were also tested. The metabolism of the bacteria was estimated by measuring their reductive capacity and by monitoring the pH and concentrations of fermentation products. Type 5 CP was always produced by S. aureus during the exponential phase of growth under all culture conditions tested. In contrast, post-exponential-phase CP production appeared to be strictly dependent on the respiratory activity. Since post-exponential-phase CP production contributes at least two-thirds of the total CP obtained, the influence of S. aureus respiration on CP production might be of some importance in the process of infection.
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Affiliation(s)
- B Dassy
- Département d'Ecologie, Insitut Pasteur, Paris, France
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209
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Goupil N, Corthier G, Ehrlich SD, Renault P. Imbalance of leucine flux in Lactococcus lactis and its use for the isolation of diacetyl-overproducing strains. Appl Environ Microbiol 1996; 62:2636-40. [PMID: 8779600 PMCID: PMC168043 DOI: 10.1128/aem.62.7.2636-2640.1996] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Diacetyl is a by-product of pyruvate metabolism in Lactococcus lactis, where pyruvate is first converted to alpha-acetolactate, which is slowly decarboxylated to diacetyl in the presence of oxygen. L. lactis usually converts alpha-acetolactate to acetoin enzymatically, by alpha-acetolactate decarboxylase encoded by the aldB gene. We took advantage of the fact that this enzyme also has a central role in the regulation of branched-chain amino acids, to select spontaneous aldB mutants in an unbalanced concentration of leucine versus those of valine and isoleucine in the medium. Industrial dairy strains of L. lactis subsp. lactis biovar diacetylactis containing point mutations and deletions of aldB were isolated and characterized. Their growth in milk was not affected, but they rapidly accumulated a large amount of alpha-acetolactate instead of acetoin from citrate in milk. Under aerated condition, strains devoid of AldB produced about 10 times more diacetyl than did the parental strains.
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Affiliation(s)
- N Goupil
- Laboratoire de Génétique Microbienne, Institut National de la Recherche Agronomique, Jouy en Josas, France
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210
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Seki A, Ortéga F, Marty JL. Enzyme Sensor for the Detection of Herbicides Inhibiting Acetolactate Synthase. ANAL LETT 1996. [DOI: 10.1080/00032719608001479] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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211
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Benson KH, Godon JJ, Renault P, Griffin HG, Gasson MJ. Effect of ilvBN-encoded α-acetolactate synthase expression on diacetyl production in Lactococcus lactis. Appl Microbiol Biotechnol 1996. [DOI: 10.1007/s002530050656] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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212
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Epelbaum S, Chipman DM, Barak Z. Metabolic effects of inhibitors of two enzymes of the branched-chain amino acid pathway in Salmonella typhimurium. J Bacteriol 1996; 178:1187-96. [PMID: 8576056 PMCID: PMC177783 DOI: 10.1128/jb.178.4.1187-1196.1996] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The metabolic effects of inhibitors of two enzymes in the pathway for biosynthesis of branched-chain amino acids were examined in Salmonella typhimurium mutant strain TV105, expressing a single isozyme of acetohydroxy acid synthase (AHAS), AHAS isozyme II. One inhibitor was the sulfonylurea herbicide sulfometuron methyl (SMM), which inhibits this isozyme and AHAS of other organisms, and the other was N-isopropyl oxalylhydroxamate (IpOHA), which inhibits ketol-acid reductoisomerase (KARI). The effects of the inhibitors on growth, levels of several enzymes of the pathway, and levels of intermediates of the pathway were measured. The intracellular concentration of the AHAS substrate 2-ketobutyrate increased on addition of SMM, but a lack of correlation between increased ketobutyrate and growth inhibition suggests that the former is not the immediate cause of the latter. The levels of the keto acid precursor of valine, but not of the precursor of isoleucine, were drastically decreased by SMM, and valine, but not isoleucine, partially overcame SMM inhibition. This apparent stronger effect of SMM on the flux into the valine arm, as opposed to the isoleucine arm, of the branched-chain amino acid pathway is explained by the kinetics of the AHAS reaction, as well as by the different roles of pyruvate, ketobutyrate, and the valine precursor in metabolism. The organization of the pathway thus potentiates the inhibitory effect of SMM. IpOHA has strong initial effects at lower concentrations than does SMM and leads to increases both in the acetohydroxy acid substrates of KARI and, surprisingly, in ketobutyrate. Valine completely protected strain TV105 from IpOHA at the MIC. A number of explanations for this effect can be ruled out, so that some unknown arrangement of the enzymes involved must be suggested. IpOHA led to initial cessation of growth, with partial recovery after a time whose duration increased with the inhibitor concentration. The recovery is apparently due to induction of new KARI synthesis, as well as disappearance of IpOHA from the medium.
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Affiliation(s)
- S Epelbaum
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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213
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Abstract
The Bacillus subtilis men genes encode biosynthetic enzymes for formation of the respiratory chain component menaquinone. The menp1 promoter previously was shown to be the primary cis element for menFD gene expression. In the present work, it was found that either supplementation with nonfermentable carbon sources or reutilization of glycolytic end products increased menp1 activity in the late postexponential phase. The effect on menp1 activity by a particular end product (such as acetoin or acetate) was prevented by blocking the corresponding pathway for end product utilization. Alteration of a TGAAA motif within the promoter region resulted in unregulated menp1 activity throughout the culture cycle, irrespective of the carbon source added.
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Affiliation(s)
- X Qin
- Wadsworth Center, New York State Department of Health, School of Public Health, State University of New York at Albany 12201-2002, USA
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214
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Park HS, Xing R, Whitman WB. Nonenzymatic acetolactate oxidation to diacetyl by flavin, nicotinamide and quinone coenzymes. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1245:366-70. [PMID: 8541313 DOI: 10.1016/0304-4165(95)00103-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Acetolactate nonenzymatically reduced flavins, quinones and nicotinamide coenzymes in a time-dependent manner at physiological pH and moderate temperature. In the presence of excess acetolactate, the reduction of FAD and NAD+ followed pseudo-first-order kinetics. The rate of reduction was proportional to the concentration of acetolactate, and the rate constants at 37 degrees C and pH 7.5 were 4.8 x 10(-2) M-1 s-1 and 7.4 x 10(-3) M-1 s-1 for FAD and NAD+, respectively. In contrast, ubiquinone reduction followed pseudo-zero-order kinetics in the presence of excess acetolactate. At 37 degrees C and pH 7.5, the rate of reduction was proportional to the acetolactate concentration, and the apparent rate constant was 8.3 x 10(-6) s-1. In contrast to FAD, the rate of reduction of ubiquinone was higher at low pH. The kinetics of ubiquinone reduction suggested that the rate-limiting step was acetolactate decarboxylation and formation of the enolate anion, whereas the rate of FAD reduction was governed by the second-order reaction of the enolate anion. Following the oxidation, acetolactate was converted to diacetyl. Reduced FAD formed by the reaction with acetolactate generated a low rate of O2 consumption during assays of the oxygenase activity of acetohydroxy acid synthase. The reaction of acetolactate with quinones may provide a mechanism for the nonenzymatic formation diacetyl in whole milk.
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Affiliation(s)
- H S Park
- Department of Microbiology, University of Georgia, Athens 30602-2605, USA
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215
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RANKIN SCOTTA, BODYFELT FLOYDW. Solvent Desorption Dynamic Headspace Method for Diacetyl and Acetoin in Buttermilk. J Food Sci 1995. [DOI: 10.1111/j.1365-2621.1995.tb04556.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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216
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Phalip V, Schmitt P, Divi�s C. Purification and characterization of the catabolic ?-acetolactate synthase from Leuconostoc mesenteroides subsp. cremoris. Curr Microbiol 1995. [DOI: 10.1007/bf00314587] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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217
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Boutsalis P, Powles SB. Inheritance and mechanism of resistance to herbicides inhibiting acetolactate synthase in Sonchus oleraceus L. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 1995; 91:242-247. [PMID: 24169770 DOI: 10.1007/bf00220884] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/1994] [Accepted: 01/27/1995] [Indexed: 06/02/2023]
Abstract
A biotype of Sonchus oleraceus L. (Compositae) has developed resistance to herbicides inhibiting acetolactate synthase (ALS) following field selection with chlorsulfuron for 8 consecutive years. The aim of this study was to determine the inheritance and mechanism of resistance in this biotype. Determination of ALS activity and inhibition kinetics revealed that Km and Vmax did not vary greatly between the resistant and susceptible biotypes. ALS extracted from the resistant biotype was resistant to five ALS-inhibiting herbicides in an in vitro assay. ALS activity from the resistant biotype was 14 19, 2, 3 and 3 times more resistant to inhibition by chlorsulfuron, sulfometuron, imazethapyr, imazapyr and flumetsulam, respectively, than the susceptible biotype. Hybrids between the resistant and a susceptible biotype were produced, and inheritance was followed through the F1, F2 and F3 generations. F1 hybrids displayed a uniform intermediate level of resistance between resistant and susceptible parents. Three distinct phenotypes, resistant, intermediate and susceptible, were identified in the F2 generation following chlorsulfuron application. A segregation ratio of 1∶2∶1 was observed, indicative of the action of a single, nuclear, incompletely dominant gene. F3 families, derived from intermediate F2 individuals, segregated in a similar manner. Resistance to herbicides inhibiting ALS in this biotype of S. oleraceus is due to the effect of a single gene coding for a resistant form of the target enzyme, ALS.
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Affiliation(s)
- P Boutsalis
- Department of Crop Protection, Waite Agricultural Research Institute, The University of Adelaide, P.M.B. 1, 5064, Glen Osmond, South Australia, Australia
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218
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Abstract
Phosphorylation of the pyruvate dehydrogenase component (E1) of the muscle pyruvate dehydrogenase complex (PDC) by E1-kinase inhibits substrate conversion both in oxidative and non-oxidative reactions. Circular dichroism spectra were used to monitor the effect of phosphorylation on the following stages of the process: holoform formation from apo-E1 and thiamine pyrophosphate (TPP), substrate binding and active site deacetylation. It has been shown that phosphorylation of E1 reduces its affinity for TPP and prevents holo-E1 interaction with pyruvate. Phosphorylated and dephosphorylated PDC convert 2-hydroxyethyl-TPP in similar ways involving half of their active sites; all active sites of E1 function in the presence of deacetylating agents. The data obtained suggest that the phosphorylation and substrate binding sites interact with each other.
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Affiliation(s)
- L G Korotchkina
- A. N. Bakh Institute of Biochemistry, Russian Academy of Sciences, Moscow
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219
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Bock AK, Schönheit P. Growth of Methanosarcina barkeri (Fusaro) under nonmethanogenic conditions by the fermentation of pyruvate to acetate: ATP synthesis via the mechanism of substrate level phosphorylation. J Bacteriol 1995; 177:2002-7. [PMID: 7721692 PMCID: PMC176842 DOI: 10.1128/jb.177.8.2002-2007.1995] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
A mutant of Methanosarcina barkeri (Fusaro) is able to grow on pyruvate as the sole carbon and energy source. During growth, pyruvate is converted to CH4 and CO2, and about 1.5 mol of ATP per mol of CH4 is formed (A.-K. Bock, A. Prieger-Kraft, and P. Schönheit, Arch. Microbiol. 161:33-46, 1994). The pyruvate-utilizing mutant of M. barkeri could also grow on pyruvate when methanogenesis was completely inhibited by bromoethanesulfonate (BES). The mutant grew on pyruvate (80 mM) in the presence of 2 mM BES with a doubling time of about 30 h up to cell densities of about 400 mg (dry weight) of cells per liter. During growth on pyruvate, the major fermentation products were acetate and CO2 (about 0.9 mol each per mol of pyruvate). Small amounts of acetoin, acetolactate, alanine, leucine, isoleucine, and valine were also detected. CH4 was not formed. The molar growth yield (Yacetate) was about 9 g of cells (dry weight) per mol of acetate, indicating an ATP yield of about 1 mol/mol of acetate formed. Growth on pyruvate in the presence of BES was limited; after six to eight generations, the doubling times increased and the final cell densities decreased. After 9 to 11 generations, growth stopped completely. In the presence of BES, suspensions of pyruvate-grown cells fermented pyruvate to acetate, CO2, and H2. CH4 was not formed. Conversion of pyruvate to acetate, in the complete absence of methanogenesis, was coupled to ATP synthesis. Dicyclohexylcarbodiimide, an inhibitor of H(+)-translocating ATP synthase, did not inhibit ATP formation. In the presence of dicyclohexylcarbodiimide, stoichiometries of up to 0.9 mol of ATP per mol of acetate were observed. The uncoupler arsenate completely inhibited ATP synthesis, while the rates of acetate, CO2, and H2 formation were stimulated up to fourfold. Cell extracts of M. barkeri grown on pyruvate under nonmethenogenic conditions contained pyruvate: ferredoxin oxidoreductase (0.5 U/mg), phosphate acetyltransferase (12 U/mg), and acetate kinase (12 U/mg). From these data it is concluded that ATP was synthesized by substrate level phosphorylation during growth of the M. barkeri mutant on pyruvate in the absence of methanogenesis. This is the first report of growth of a methanogen under nonmethanogenic conditions at the expense of a fermentative energy metabolism.
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Affiliation(s)
- A K Bock
- Institut für Pflanzenphysiologie und Mikrobiologie, Fachbereich Biologie, Freie Universität Berlin, Germany
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220
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ter Steeg P, Pieterman F, Hellemons J. Effects of air/nitrogen, temperature and pH on energy-dependent growth and survival of Listeria innocua in continuous culture and water-in-oil emulsions. Food Microbiol 1995. [DOI: 10.1016/s0740-0020(95)80132-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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221
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Durner J, Gailus V, Böger P. The oxygenase reaction of acetolactate synthase detected by chemiluminescence. FEBS Lett 1994; 354:71-3. [PMID: 7957905 DOI: 10.1016/0014-5793(94)01097-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In addition to the synthesis of ketolacids the enzyme acetolactate synthase shows an oxygen-consuming side reaction. Partially purified acetolactate synthase from corn (Zea mays L.) and barley (Hordeum vulgare L.) exhibits chemiluminescence in the presence of oxygen, Mn2+ and low concentrations of pyruvate. Light emission is inhibited by azide, but not by catalse or superoxide dismutase. The data suggest the formation of singlet oxygen during the catalytic cycle, and provides a basis for a highly sensitive assay for the oxygenase reaction of acetolactate synthesis. Both synthase activity and chemiluminescence are inhibited by sulfonylurea herbicides. The results add a new aspect to the irreversible inhibition of acetolactate synthase by these herbicides which may be enhanced by the presence of reactive oxygen species.
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Affiliation(s)
- J Durner
- Lehrstuhl für Physiologie und Biochemie, Pflanzen Universität Konstanz, Germany
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222
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Monnet C, Schmilt P, Divies C. Diacetyl Production in Milk by an α-Acetolactic Acid Accumulating Strain of Lactococcus lactis ssp. lactis biovar. diacetylactis. J Dairy Sci 1994. [DOI: 10.3168/jds.s0022-0302(94)77232-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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223
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Phalip V, Monnet C, Schmitt P, Renault P, Godon JJ, Diviès C. Purification and properties of the alpha-acetolactate decarboxylase from Lactococcus lactis subsp. lactis NCDO 2118. FEBS Lett 1994; 351:95-9. [PMID: 8076701 DOI: 10.1016/0014-5793(94)00820-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
alpha-Acetolactate decarboxylase from Lactococcus lactis subsp. lactis NCDO 2118 was expressed at low levels in cell extracts and was also unstable. The purification was carried out from E. coli in which the enzyme was expressed 36-fold higher. The specific activity was 24-fold enhanced after purification. The main characteristics of alpha-acetolactate decarboxylase were: (i) activation by the three branched chain amino acids leucine, valine and isoleucine; (ii) allosteric properties displayed in absence and Michaelis kinetics in the presence of leucine. The enzyme is composed of six identical subunits of 26,500 Da.
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Affiliation(s)
- V Phalip
- Laboratoire de Microbiologie, ENS.BANA, Dijon, France
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224
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Zinebi S, Raval G, Petitdemange H. Effect of oxygenation and sulfate concentrations on pyruvate and lactate formation inKlebsiella oxytoca ZS growing in chemostat cultures. Curr Microbiol 1994. [DOI: 10.1007/bf01575752] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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225
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Cachon R, Divi�s C. Generalized model of the effect of pH on lactate fermentation and citrate bioconversion in Lactococcus lactis ssp. Lactis biovar. diacetylactis. Appl Microbiol Biotechnol 1994. [DOI: 10.1007/bf00167287] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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226
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Monnet C, Schmitt P, Divies C. Method for Assaying Volatile Compounds by Headspace Gas Chromatography and Application to Growing Starter Cultures. J Dairy Sci 1994. [DOI: 10.3168/jds.s0022-0302(94)77122-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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227
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Ramos A, Jordan KN, Cogan TM, Santos H. 13
C Nuclear Magnetic Resonance Studies of Citrate and Glucose Cometabolism by
Lactococcus lactis. Appl Environ Microbiol 1994; 60:1739-48. [PMID: 16349269 PMCID: PMC201556 DOI: 10.1128/aem.60.6.1739-1748.1994] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
13
C nuclear magnetic resonance (
13
C-NMR) was used to investigate the metabolism of citrate plus glucose and pyruvate plus glucose by nongrowing cells of
Lactococcus lactis
subsp.
lactis
19B under anaerobic conditions. The metabolism of citrate plus glucose during growth was also monitored directly by in vivo NMR. Although pyruvate is a common intermediate metabolite in the metabolic pathways of both citrate and glucose, the origin of the carbon atoms in the fermentation products was determined by using selectively labeled substrates, e.g., [2,4-
13
C]citrate, [3-
13
C]pyruvate, and [2-
13
C]glucose. The presence of an additional substrate caused a considerable stimulation in the rates of substrate utilization, and the pattern of end products was changed. Acetate plus acetoin and butanediol represented more than 80% (molar basis) of the end products of the metabolism of citrate (or pyruvate) alone, but when glucose was also added, 80% of the citrate (or pyruvate) was converted to lactate. This result can be explained by the activation of lactate dehydrogenase by fructose 1,6-bisphosphate, an intermediate in glucose metabolism. The effect of different concentrations of glucose on the metabolism of citrate by dilute cell suspensions was also probed by using analytical methods other than NMR. Pyruvate dehydrogenase (but not pyruvate formate-lyase) was active in the conversion of pyruvate to acetyl coenzyme A. α-Acetolactate was detected as an intermediate metabolite of citrate or pyruvate metabolism, and the labeling pattern of the end products agrees with the α-acetolactate pathway. It was demonstrated that the contribution of the acetyl coenzyme A pathway for the synthesis of diacetyl, should it exist, is lower than 10%. Evidence for the presence of internal carbon reserves in
L. lactis
is presented.
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Affiliation(s)
- A Ramos
- Instituto de Tecnologia Química e Biológica/Instituto de Biologia Experimental e Tecnológica, 2780 Oeiras, Portugal
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228
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Meisel J, Wolf G, Hammes WP. Heme-Dependent Cytochrome Formation in Lactobacillus maltaromicus. Syst Appl Microbiol 1994. [DOI: 10.1016/s0723-2020(11)80026-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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229
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Comparison of ?-acetolactate synthase and ?-acetolactate decarboxylase in Lactococcus spp. and Leuconostoc spp. Biotechnol Lett 1994. [DOI: 10.1007/bf00134622] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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230
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231
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Phalip V, Schmitt P, Diviès C. A method for screening diacetyl and acetoin-producing bacteria on agar plates. J Basic Microbiol 1994. [DOI: 10.1002/jobm.3620340412] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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232
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Stivers JT, Washabaugh MW. Catalysis of acetoin formation by brewers' yeast pyruvate decarboxylase isozymes. Biochemistry 1993; 32:13472-82. [PMID: 8257682 DOI: 10.1021/bi00212a012] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Catalysis of C(alpha)-proton transfer from 2-(1-hydroxyethyl)thiamin diphosphate (HETDP) by pyruvate decarboxylase isozymes (PDC; EC 4.1.1.1) from Saccharomyces carlsbergensis was investigated by determining the steady-state kinetics of the reaction of [1-L]acetaldehyde (L = H, D, or T) to form acetoin and the primary kinetic isotope effects on the reaction. The PDC isozyme mixture and alpha 4 isozyme (alpha 4-PDC) have different steady-state kinetic parameters and isotope effects for acetoin formation in the presence and absence of the nonsubstrate allosteric effector pyruvamide: pyruvamide activation occurs by stabilization of the acetaldehyde/PDC ternary complex. The magnitudes of primary L(V/K)-type (L = D or T) isotope effects on C(alpha)-proton transfer from alpha 4-PDC-bound HETDP provide no evidence for significant breakdown of the Swain-Schaad relationship that would indicate partitioning of the putative C(alpha)-carbanion/enamine intermediate between HETDP and products. The substrate concentration dependence of the deuterium primary kinetic isotope effects provides evidence for an intrinsic isotope effect of 4.1 for C(alpha)-proton transfer from alpha 4-PDC-bound HETDP. A 1.10 +/- 0.02-fold 14C isotope discrimination against [1,2-14C]acetaldehyde in acetoin formation is inconsistent with a stepwise mechanism, in which the addition step occurs after rate-limiting formation of the C(alpha)-carbanion/enamine as a discrete enzyme-bound intermediate, and provides evidence for a concerted reaction mechanism with an important component of carbon-carbon bond formation in the transition state.
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Affiliation(s)
- J T Stivers
- Department of Biochemistry, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland 21205-2179
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233
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Hugenholtz J, Perdon L, Abee T. Growth and Energy Generation by
Lactococcus lactis
subsp.
lactis
biovar diacetylactis during Citrate Metabolism. Appl Environ Microbiol 1993; 59:4216-22. [PMID: 16349120 PMCID: PMC195888 DOI: 10.1128/aem.59.12.4216-4222.1993] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Growth of
Lactococcus lactis
subsp.
lactis
biovar diacetylactis was observed on media with citrate as the only energy source. At pH 5.6, steady state was achieved in a chemostat on a citrate-containing medium in the absence of a carbohydrate. Under these conditions, pyruvate, acetate, and some acetoin and butanediol were the main fermentation products. This indicated that energy was conserved in
L. lactis
subsp.
lactis
biovar diacetylactis during citrate metabolism and presumably during the conversion of citrate into pyruvate. The presumed energy-conserving step, decarboxylation of oxaloacetate, was studied in detail. Oxaloacetate decarboxylase was purified to homogeneity and characterized. The enzyme has a native molecular mass of approximately 300 kDa and consists of three subunits of 52, 34, and 12 kDa. The enzyme is apparently not sodium dependent and does not contain a biotin moiety, and it seems to be different from the energy-generating oxaloacetate decarboxylase from
Klebsiella pneumoniae.
Energy-depleted
L. lactis
subsp.
lactis
biovar diacetylactis cells generated a membrane potential and a pH gradient immediately upon addition of citrate, whereas ATP formation was slow and limited. In contrast, lactose energization resulted in rapid ATP formation and gradual generation of a proton motive force. These data were confirmed during studies on amino acid uptake. α-Aminoisobutyrate uptake was rapid but glutamate uptake was slow in citrate-energized cells, whereas lactose-energized cells showed the reverse tendency. These data suggest that, in
L. lactis
subsp.
lactis
bv. diacetylactis, a proton motive force could be generated during citrate metabolism as a result of electrogenic citrate uptake or citrate/product exchange together with proton consumption by the intracellular oxaloacetate decarboxylase.
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Affiliation(s)
- J Hugenholtz
- Netherlands Institute for Dairy Research (NIZO), 6710 BA Ede, and Department of Food Science, Agricultural University of Wageningen, Wageningen, The Netherlands
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234
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Cachon R, Divies C. Localization of Lactococcus lactis ssp lactis bv diacetylactis in alginate gel beads affects biomass density and synthesis of several enzymes involved in lactose and citrate metabolism. ACTA ACUST UNITED AC 1993. [DOI: 10.1007/bf00155479] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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235
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Spectrophotometric determination of total vicinal diketones with isoniazide and a zirconium salt. ACTA ACUST UNITED AC 1993. [DOI: 10.1007/bf00323972] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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236
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Weinstock O, Sella C, Chipman DM, Barak Z. Properties of subcloned subunits of bacterial acetohydroxy acid synthases. J Bacteriol 1992; 174:5560-6. [PMID: 1512191 PMCID: PMC206499 DOI: 10.1128/jb.174.17.5560-5566.1992] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The acetohydroxy acid synthase (AHAS) isozymes from enterobacteria are each composed of a large and small subunit in an alpha 2 beta 2 structure. It has been generally accepted that the large (ca. 60-kDa) subunits are catalytic, while the small ones are regulatory. In order to further characterize the roles of the subunits as well as the nature and the specificities of their interactions, we have constructed plasmids encoding the large or small subunits of isozymes AHAS I and AHAS III, each with limited remnants of the other peptide. The catalytic properties of the large subunits have been characterized and compared with those of extracts containing the intact enzyme or of purified enzymes. Antisera to the isolated subunits have been used in Western blot (immunoblot) analyses for qualitative and semiquantitative determinations of the presence of the polypeptides in extracts. The large subunits of AHAS isozymes I and III have lower activities than the intact enzymes: Vmax/Km is 20 to 50 times lower in both cases. However, for AHAS I, most of this difference is due to the raised Km of the large subunit alone, while for AHAS III, it is due to a lowered Vmax. The substrate specificities, R, of large subunits are close to those of the intact enzymes. The catalytic activity of the large subunits of AHAS I is dependent on flavin adenine dinucleotide (FAD), as is that of the intact enzyme, although the apparent affinities of the large subunits alone for FAD are 10-fold lower. Isolated subunits are insensitive to valine inhibition. Nearly all of the properties of the intact AHAS isozyme I or III can be reconstituted by mixing extracts containing the respective large and small subunits. The mixing of subunits from different enzymes does not lead to activation of the large subunits. It is concluded that the catalytic machinery of these AHAS isozymes is entirely contained within the large subunits. The small subunits are required, however, for specific stabilization of an active conformation of the large subunits as well as for value sensitivity.
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Affiliation(s)
- O Weinstock
- Department of Life Sciences, Ben Gurion University of the Negev, Beer Sheva, Israel
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237
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Otsuka M, Ohmori S. Simple and sensitive determination of diacetyl and acetoin in biological samples and alcoholic drinks by gas chromatography with electron-capture detection. JOURNAL OF CHROMATOGRAPHY 1992; 577:215-20. [PMID: 1400754 DOI: 10.1016/0378-4347(92)80242-i] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Acetoin was quantitatively oxidized into diacetyl by Fe3+ in 1 M perchloric acid. The reaction of diacetyl with 4,5-dichloro-1,2-diaminobenzene afforded 6,7-dichloro-2,3-dimethylquinoxaline (DCDMQ), which was extracted by benzene containing aldrin (25 ng/ml) as an internal standard, and determined by gas chromatography with electron-capture detection. The method is very simple and sensitive. The detection limit of DCDMQ (either diacetyl or acetoin) was 10 fmol/microliters of the benzene extract, and the determination limit of DCDMQ (either diacetyl or acetoin) was 50 fmol/microliters of the extract. Both acetoin and diacetyl could be determined in 0.1 ml of normal human urine or blood, and both were found in rat liver, kidney and brain. The method was also applied to the determination of acetoin and diacetyl in alcoholic drinks.
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Affiliation(s)
- M Otsuka
- Faculty of Pharmaceutical Sciences, Okayama University, Japan
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238
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Use of starter cultures containingStreptococcus diacetilactis, Lactobacillus brevis andSaccharomyces cerevisiae for fermenting milk for production of Nigeriannono. World J Microbiol Biotechnol 1992; 8:251-3. [DOI: 10.1007/bf01201872] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/1991] [Accepted: 10/11/1991] [Indexed: 10/25/2022]
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239
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240
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Marcussen J, Poulsen C. A nondestructive method for peptide bond conjugation of antigenic haptens to a diphtheria toxoid carrier, exemplified by two antisera specific to acetolactate synthase. Anal Biochem 1991; 198:318-23. [PMID: 1799217 DOI: 10.1016/0003-2697(91)90432-s] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A method for the preparation of an activated protein carrier is described: Protein carboxyl groups are transformed into N-hydroxysulfosuccinimide esters, a structure that will react with primary amino groups under amide bond formation. Although the activated ester is unstable under aqueous conditions, a significant amount of hapten molecules can be bound covalently to the carrier under very mild conditions. Ligands can be peptides or other molecules possessing a primary amino group. The method avoids the risk of ligand polymerization and no derivatization of the ligand prior to conjugation is needed. Residual unreacted ligand molecules can therefore be recovered in their native form by size exclusion chromatography. The method was used to conjugate two synthetic sugar beet acetolactate synthetase (E.C. 4.1.3.18) peptides to diphtheria toxoid. Antibodies were raised against both of the conjugates. The specificity of these antibodies against sugar beet acetolactate synthetase was verified using immunoblotting, ELISA, and immunoprecipitation.
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Affiliation(s)
- J Marcussen
- Danisco A/S, Biotechnology Research Division, Copenhagen, Denmark
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241
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Forlani G, Riccardi G, De Rossi E, De Felice M. Biochemical evidence for multiple forms of acetohydroxy acid synthase in Spirulina platensis. Arch Microbiol 1991. [DOI: 10.1007/bf00252216] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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242
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Lin J, Schmitt P, Diviès C. Characterization of a citrate-negative mutant ofLeuconostoc mesenteroides subsp.mesenteroides: metabolic and plasmidic properties. Appl Microbiol Biotechnol 1991. [DOI: 10.1007/bf00167912] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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243
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Gibson TD, Parker SM, Woodward JR. Purification and characterization of diacetyl reductase from chicken liver and Streptococcus lactis and enzymic determination of diacetyl and diketones. Enzyme Microb Technol 1991. [DOI: 10.1016/0141-0229(91)90175-a] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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244
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Nikolova P, Long A, Ward OP. Colorimetric determination of L-phenylacetyl carbinol produced by biotransformation of benzaldehyde and pyruvate using Saccharomyces cerevisiae. ACTA ACUST UNITED AC 1991. [DOI: 10.1007/bf00152751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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245
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Hagrass AE, Fayed EO, Aly AA, el-Samragy YA. Growth characteristics of enterococci isolated from Laban Rayeb. DIE NAHRUNG 1991; 35:209-13. [PMID: 1904991 DOI: 10.1002/food.19910350216] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Eleven strains of Enterococcus (Streptococcus) faecalis isolated from Laban Rayeb, a type of fermented milk, had been studied when grew in milk. Enterococcus (Streptococcus) faecalis strains 19 and 22 were the most active strains in the production of lactic acid, acetaldehyde and diacetyl. Both strains exhibited a high proteolytic activity besides a good clean flavour. Based on the obtained results, Enterococcus (Streptococcus) faecalis 19 and 22 could be used to bring about the lactic fermentation during the manufacture of some cultured dairy products.
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Affiliation(s)
- A E Hagrass
- Food Science Department, Faculty of Agriculture, Ain Shams University, Shobra El-Khima, Cairo, Egypt
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246
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247
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Epelbaum S, Chipman DM, Barak Z. Determination of products of acetohydroxy acid synthase by the colorimetric method, revisited. Anal Biochem 1990; 191:96-9. [PMID: 2077946 DOI: 10.1016/0003-2697(90)90393-n] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The enzyme acetohydroxy acid synthase (AHAS, EC 4.1.3.18) catalyzes two competing reactions of physiological importance: condensation of two molecules of pyruvate to form acetolactate (AL) or condensation of pyruvate and 2-ketobutyrate to form acetohydroxybutyrate (AHB). The activity of AHAS is most frequently analyzed using the Westerfeld method, in which the acetoin formed upon decarboxylation of AL is determined by colorimetric reaction with creatine and alpha-naphthol. However, there has been confusion as to the interpretation of the results of this assay in the presence of both substrates, conditions which lead to formation of both AL and AHB. By applying this assay to enzymatically prepared samples of AL and AHB which have also been analyzed by two other independent methods, we show here that the color yield for AHB in the commonly used assay is 35-40% that for equivalent amounts of acetoin or AL. The relative color yield is not significantly affected by varying the time or temperature of various steps in the color-forming reaction. This information could in principle be used, together with an independent specific assay for AHB, to determine the composition of an AHAS product mixture; it would, however, be less accurate than a simultaneous chromatographic method.
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Affiliation(s)
- S Epelbaum
- Department of Biology, Ben-Gurion University, Beer-Sheva, Israel
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248
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Wiersma PA, Hachey JE, Crosby WL, Moloney MM. Specific truncations of an acetolactate synthase gene from Brassica napus efficiently complement ilvB/ilvG mutants of Salmonella typhimurium. MOLECULAR & GENERAL GENETICS : MGG 1990; 224:155-9. [PMID: 2277630 DOI: 10.1007/bf00259463] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The expression of an acetolactate synthase (ALS) gene isolated from the cruciferous plant Brassica napus was investigated in Salmonella typhimurium. Using an expression plasmid containing the highly active trc (trp-lac) promoter, several plant ALS constructs were made containing successive in-frame truncations from the 5' end of the coding region. Functional complementation by these plant ALS constructs of a S. typhimurium mutant devoid of ALS enzymic activity was assayed on minimal medium. Truncations which eliminated a large portion of the transit peptide coding sequence proved to act as efficient ALS genes in the bacterial host. Truncations close to the putative processing site of the plant protein were inactive in the complementation test. A full length copy of the gene, including the entire transit peptide coding region, was also inactive. The efficiency of the complementation, estimated by comparison to the growth rate of wild-type S. typhimurium, was found to correlate with levels of ALS activity in the transformed bacteria. Specific mutations, known to produce herbicide resistance in plants, were introduced into the truncated ALS coding sequence by site-directed mutagenesis. When expressed in bacteria these constructs conferred a herbicide resistance phenotype on the host. The potential of this system for mutagenesis and enzymological studies of plant proteins is discussed.
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Affiliation(s)
- P A Wiersma
- Department of Biological Sciences, University of Calgary, Alberta, Canada
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249
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Production of 2,3-butanediol from wood hydrolysate byKlebsiella pneumoniae. World J Microbiol Biotechnol 1990; 6:328-32. [DOI: 10.1007/bf01201306] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/1989] [Revised: 03/12/1990] [Accepted: 03/25/1990] [Indexed: 10/25/2022]
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250
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PARISH MICKEYE, BRADDOCK ROBERTJ, WICKER LOUISE. GAS CHROMATOGRAPHIC DETECTION OF DIACETYL IN ORANGE JUICE. J FOOD QUALITY 1990. [DOI: 10.1111/j.1745-4557.1990.tb00021.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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