Zur Biochemie der Threonin‐Desaminase aus Hefe

Holzer, Helmut; Boll, Matthias; Cennamo, C.

doi:10.1002/ange.19630751903

Cited by 44 publications

(14 citation statements)

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“…The existence, in allosteric enzymes, of many ligands, with independent sites of attachment and nzyces cerevisiae have shown this enzyme to be closely related to the bacterial enzyme as far as its catalytic and allosteric properties are concerned [7,8]. I n addition, we now find that the molecular weight of the yeast enzyme is similar to the molecular weight recently determined for the pure threonine deaminase from Salmonella [9, lo].…”

supporting

confidence: 74%

“…The yeast enzyme has a t least four amino acid ligands: (a) the substrate, threonine, (b) the endproduct inhibitor, isoleucine, (c) the activator valine, end-product of the parallel pathway [7,8], (d) the substrate analogue, and non-allosteric inhibitor, allothreonine (see below). I n addition, the inorganic product of the reaction, ammonium ion, is a potent activator of the yeast enzyme [ll].…”

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confidence: 99%

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Regulation of Isoleucine-Valine Biosynthesis in Saccharomyces cerevisiae

Brunner

Devillers-Mire

Robichon-Szulmajster

2005

European Journal of Biochemistry

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An isoleucine requiring mutant (M6) of Saccharomyces cerevisiae was found to have an altered threonine deaminase. The mutation maps in the is, locus which corresponds to a threonine deaminase deficiency in other isoleucine requiring mutants.Both the molecular weight and the absolute number of sites for the ligands remain the same in the wild type and the mutant enzyme.The following catalytic and regulatory properties are modified in the mutant enzyme :1. Affinity towards threonine is 4 to 6 fold lower. Also, in contrast with the wild type, co-2. Affinity towards the substrate analogue (competitive inhibitor), allothreonine, is 2 to 3 fold 3. Affinity towards a feedback inhibitor, isoleucine, is increased by 5 to 6 fold. 4.Valine remains active as a positive effector (suppressing the cooperativity between substrate molecules) but a 20 fold higher concentration is required for a 50°/, maximal effect. On the other hand, a t high concentrations, valine is inhibitory. The apparent Ka, a t substrate saturation, is 36 mM. The changes in kinetic properties of the mutant enzyme, which occurred for each individual ligand in the most unfavorable direction, can explain its complete inefficiency in vivo, and account for the isoleucine requirement of the mutant strain. Growth studies have shown that the impaired enzyme can, in vivo, utilize exogenous threonine and be activated by exogenously supplied valine.These results have been interpreted as an indication that endogenous threonine and valine concentrations were the factors responsible for the mutant inability to grow in minimal medium.

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confidence: 74%

mentioning

confidence: 99%

Regulation of Isoleucine-Valine Biosynthesis in Saccharomyces cerevisiae

Brunner

Devillers-Mire

Robichon-Szulmajster

2005

European Journal of Biochemistry

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“…Threonine dehydratase activity was determined using a coupled optical test with NADH, and lactate dehydrogenase described by Holzer et al [3,5]. The "standard buffer" used in the purification procedure contained 0.05 M potassium phosphate pH 7.6, 1 mM pyridoxal 5-phosphate, 0.1 mM EDTA, 1 mM mercaptoethanol, and 50 pM L-valine.…”

Section: Nethodsmentioning

confidence: 99%

“…Threonine dehydratase from yeast, like that from E . coli, is inhibited by isoleucine and activated by valine [3]. Furthermore, enzymatic activity in crude extracts is stabilized by pyridoxal phosphate, protected by threonine, valine and isoleucine against inactivation upon dilution, and enhanced by ammonium ions [3-61. Prerequisite to the further investigation of the regulatory properties of this enzyme is its availability in pure form.…”

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confidence: 99%

Purification and Some Properties of Threonine Dehydratase from Yeast

Katsunuma

Elsässer

Holzer

1971

European Journal of Biochemistry

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Biosynthetic L‐threonine dehydratase was purified from bakers' yeast and crystallized. The enzyme was homogeneous as judged by ultracentrifugation and electrophoresis. s20, was 9.2 S, and the molecular weight was estimated to be approximately 185000. The enzyme exhibits a slight yellow color. An absorption maximum in the visible region was at 410 nm. Apparent Michaelis constants for L‐threonine and L‐serine are reported.

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“…The first enzyme in the pathway leading to the formation ofisoleucine is threonine deaminase, an allosteric enzyme converting threonine to a-ketobutyrate (7,8,9,25). The four following enzymatic steps, converting ct-ketobutyrate plus pyruvate to isoleucine, and pyruvate to valine, are shared by the two pathways.…”

Section: Introducrionmentioning

confidence: 99%

Mutational analysis of isoleucine-valine biosynthesis in Saccharomyces cerevisiae. Mapping ofilv2 andilv5

Petersen

Kielland‐Brandt

Holmberg

et al. 1983

Carlsberg Res. Commun.

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Keywords: Yeast, branched-chain a m i n o acids, tetrad analysis, spoil mapping, c h r o m o s o m e loss, genetic c o m p l e m e n t a t i o n , ribosomal DNA, ct-acetohydroxyacids, vicinal diketones Fifty-five isoleucine-valine requiring mutants were selected in a haploid strain of Saccharomyces cerevisiae after treatment with ethyl methanesulfonate. All the mutants could be assigned to the known complementation groups, ilvl (threonine deaminase), ilv2 (acetohydroxyacid synthetase), ilv5 (acetohydroxyacid reductoisomerase) and ilv3 (dihydroxyacid dehydrase). Intragenic complementation occurs in both ilv2 and ilv5. The levels of aacetohydroxyacids formed by these four types of mutants were consistent with the previous notion that the mutants define the structural genes coding for these enzymes.Chromosome assignment by the Rec-(spoll) mapping method showed that ilv2 was located on chromosome XIII, and ilv5 on chromosome XII. The locations were confirmed by mitotic analyses, using either tad52 homozygosis or benzimidazol carbamic acid methyl ester. Tetrad analysis placed ilv2 on the right arm of chromosome XIII, 36 cM distal to lysT, and ilv5 was positioned on the right arm of chromosome XII, distal to the ribosomal RNA gene cluster (rDNA) and proximal to ura4.Abbreviations: can = L-canavanine sulfate; cyh = cycloheximide; EMS = ethyl methanesulfonate; MBC = benzimidazol-2-ylcarbamic acid methyl ester; MMS = methyl methanesulfonate; NPD = non-parental ditype; PD = parental ditype; T = tetratype.

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Zur Biochemie der Threonin‐Desaminase aus Hefe

Cited by 44 publications

References 8 publications

Regulation of Isoleucine-Valine Biosynthesis in Saccharomyces cerevisiae

Regulation of Isoleucine-Valine Biosynthesis in Saccharomyces cerevisiae

Purification and Some Properties of Threonine Dehydratase from Yeast

Mutational analysis of isoleucine-valine biosynthesis in Saccharomyces cerevisiae. Mapping ofilv2 andilv5

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