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Literature summary for 2.2.1.6 extracted from

  • DeFelice, M.; Squires, C.; Levinthal, M.
    A comparative study of the acetohydroxy acid synthase isoenzymes of Escherichia coli K-12 (1978), Biochim. Biophys. Acta, 541, 9-17.
No PubMed abstract available

General Stability

General Stability Organism
dialysis causes 38% loss of activity of isoenzyme I, stimulates activity of isoenzyme III Escherichia coli

Inhibitors

Inhibitors Comment Organism Structure
2-oxobutanoate isoenzyme I has lower sensitivity to inhibition than isoenzyme III Escherichia coli
Val isoenzyme I is more resistant to inhibition than isoenzyme III Escherichia coli

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
1.3
-
pyruvate isoenzyme I Escherichia coli
7.6
-
pyruvate isoenzyme III Escherichia coli

Metals/Ions

Metals/Ions Comment Organism Structure
Mg2+ required Escherichia coli
Mg2+ Km: 0.3 mM for isoenzyme I, 0.4 mM for isoenzyme III Escherichia coli

Organism

Organism UniProt Comment Textmining
Escherichia coli
-
K-12
-
Escherichia coli
-
wild type and two isogenic strains PS1035, containing only acetohydroxy acid synthase III, and strain PS1036, containing only acetohydroxy acid synthase I
-

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
pyruvate
-
Escherichia coli 2-acetolactate + CO2
-
?

Temperature Stability [°C]

Temperature Stability Minimum [°C] Temperature Stability Maximum [°C] Comment Organism
45
-
15 min, 69% loss of activity, isoenzyme I, slight stimulation of activity of isoenzyme III Escherichia coli

Cofactor

Cofactor Comment Organism Structure
FAD required by isoenzyme I, no requirement by isoenzyme III Escherichia coli
FAD Km: 0.00016 mM for isoenzyme I Escherichia coli
thiamine diphosphate required as cofactor Escherichia coli
thiamine diphosphate Km: 0.0087 mM for isoenzyme I, 0.026 mM for isoenzyme III Escherichia coli