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Literature summary for 4.2.1.22 extracted from

  • Aitken, S.M.; Kirsch, J.F.
    Role of active-site residues Thr81, Ser82, Thr85, Gln157, and Tyr158 in yeast cystathionine beta-synthase catalysis and reaction specificity (2004), Biochemistry, 43, 1963-1971.
    View publication on PubMed

Protein Variants

Protein Variants Comment Organism
Q157A no detectable beta-replacement activity, catalyzes a competing beta-elimination reaction, in which L-Ser is hydrolyzed to NH3 and pyruvate Saccharomyces cerevisiae
Q157E no detectable beta-replacement activity, catalyzes a competing beta-elimination reaction, in which L-Ser is hydrolyzed to NH3 and pyruvate Saccharomyces cerevisiae
Q157H enzyme suffers suicide inhibition via a mechanism in which the released aminoacrylate intermediate covalently attacks the internal aldimine of the enzyme, catalyzes a competing beta-elimination reaction, in which L-Ser is hydrolyzed to NH3 and pyruvate Saccharomyces cerevisiae
S82A catalyzes a competing beta-elimination reaction, in which L-Ser is hydrolyzed to NH3 and pyruvate Saccharomyces cerevisiae
T81A catalyzes a competing beta-elimination reaction, in which L-Ser is hydrolyzed to NH3 and pyruvate Saccharomyces cerevisiae
T85A catalyzes a competing beta-elimination reaction, in which L-Ser is hydrolyzed to NH3 and pyruvate Saccharomyces cerevisiae
Y158F 3fold decreased beta-replacement activity, enzyme suffers suicide inhibition via a mechanism in which the released aminoacrylate intermediate covalently attacks the internal aldimine of the enzyme, catalyzes a competing beta-elimination reaction, in which L-Ser is hydrolyzed to NH3 and pyruvate Saccharomyces cerevisiae

Organism

Organism UniProt Comment Textmining
Saccharomyces cerevisiae
-
-
-

Reaction

Reaction Comment Organism Reaction ID
L-serine + L-homocysteine = L-cystathionine + H2O ping-pong mechanism Saccharomyces cerevisiae

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
L-serine + H2O wild-type enzyme shows no beta-elimination reaction, beta elimination is only detectable in the following mutants: T81A, S82A, T85A, Q157A, Q157E, Q157H, Y158F Saccharomyces cerevisiae NH3 + pyruvate
-
?
L-Serine + homocysteine
-
Saccharomyces cerevisiae Cystathionine + H2O
-
r

Turnover Number [1/s]

Turnover Number Minimum [1/s] Turnover Number Maximum [1/s] Substrate Comment Organism Structure
0.082
-
L-serine Q157H mutant, pH 8.6, 37°C Saccharomyces cerevisiae
0.083
-
L-cystathionine S82A mutant, pH 8.6, 37°C Saccharomyces cerevisiae
0.133
-
L-cystathionine T85A mutant, pH 8.6, 37°C Saccharomyces cerevisiae
0.418
-
L-cystathionine Y158F mutant, pH 8.6, 37°C Saccharomyces cerevisiae
0.45
-
L-serine T81A mutant, pH 8.6, 37°C Saccharomyces cerevisiae
0.56
-
L-cystathionine wild-type enzyme, pH 8.6, 37°C Saccharomyces cerevisiae
5.3
-
L-serine S82A mutant, pH 8.6, 37°C Saccharomyces cerevisiae
6.08
-
L-cystathionine wild-type enzyme, pH 8.6, 37°C Saccharomyces cerevisiae
8.2
-
L-serine Y158F mutant, pH 8.6, 37°C Saccharomyces cerevisiae
13.2
-
L-serine T85A mutant, pH 8.6, 37°C Saccharomyces cerevisiae
21.5
-
L-serine wild-type enzyme, pH 8.6, 37°C Saccharomyces cerevisiae