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Literature summary 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

EC Number Protein Variants Comment Organism
4.2.1.22 Q157A no detectable beta-replacement activity, catalyzes a competing beta-elimination reaction, in which L-Ser is hydrolyzed to NH3 and pyruvate Saccharomyces cerevisiae
4.2.1.22 Q157E no detectable beta-replacement activity, catalyzes a competing beta-elimination reaction, in which L-Ser is hydrolyzed to NH3 and pyruvate Saccharomyces cerevisiae
4.2.1.22 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
4.2.1.22 S82A catalyzes a competing beta-elimination reaction, in which L-Ser is hydrolyzed to NH3 and pyruvate Saccharomyces cerevisiae
4.2.1.22 T81A catalyzes a competing beta-elimination reaction, in which L-Ser is hydrolyzed to NH3 and pyruvate Saccharomyces cerevisiae
4.2.1.22 T85A catalyzes a competing beta-elimination reaction, in which L-Ser is hydrolyzed to NH3 and pyruvate Saccharomyces cerevisiae
4.2.1.22 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

EC Number Organism UniProt Comment Textmining
4.2.1.22 Saccharomyces cerevisiae
-
-
-

Reaction

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

Substrates and Products (Substrate)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
4.2.1.22 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
-
 ?
4.2.1.22 L-Serine + homocysteine
-
 Saccharomyces cerevisiae Cystathionine + H2O
-
 r

Turnover Number [1/s]

EC Number Turnover Number Minimum [1/s] Turnover Number Maximum [1/s] Substrate Comment Organism Structure
4.2.1.22 0.082
-
 L-serine Q157H mutant, pH 8.6, 37°C Saccharomyces cerevisiae
4.2.1.22 0.083
-
 L-cystathionine S82A mutant, pH 8.6, 37°C Saccharomyces cerevisiae
4.2.1.22 0.133
-
 L-cystathionine T85A mutant, pH 8.6, 37°C Saccharomyces cerevisiae
4.2.1.22 0.418
-
 L-cystathionine Y158F mutant, pH 8.6, 37°C Saccharomyces cerevisiae
4.2.1.22 0.45
-
 L-serine T81A mutant, pH 8.6, 37°C Saccharomyces cerevisiae
4.2.1.22 0.56
-
 L-cystathionine wild-type enzyme, pH 8.6, 37°C Saccharomyces cerevisiae
4.2.1.22 5.3
-
 L-serine S82A mutant, pH 8.6, 37°C Saccharomyces cerevisiae
4.2.1.22 6.08
-
 L-cystathionine wild-type enzyme, pH 8.6, 37°C Saccharomyces cerevisiae
4.2.1.22 8.2
-
 L-serine Y158F mutant, pH 8.6, 37°C Saccharomyces cerevisiae
4.2.1.22 13.2
-
 L-serine T85A mutant, pH 8.6, 37°C Saccharomyces cerevisiae
4.2.1.22 21.5
-
 L-serine wild-type enzyme, pH 8.6, 37°C Saccharomyces cerevisiae