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Phosphoserine Aminotransferase, the Second Step‐Catalyzing Enzyme for Serine Biosynthesis
Author(s) -
Basurko MarieJose,
Marche Michele,
Darriet Monique,
Cassaigne Andre
Publication year - 1999
Publication title -
iubmb life
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.132
H-Index - 113
eISSN - 1521-6551
pISSN - 1521-6543
DOI - 10.1080/713803557
Subject(s) - phosphoserine , serine , enzyme , biosynthesis , biochemistry , chemistry , cofactor , stereochemistry , biology
As a step toward analyzing the serine biosynthetic pathway in mammals, we have studied the properties of phosphoserine aminotransferase, the second step‐catalyzing enzyme. The Km values for 3‐phosphohydroxypyruvate and L‐phosphoserine are 5 and 35 mu M, respectively, and those for glutamate and alpha‐ketoglutarate are 1.2 and 0.8 mM, respectively. The product inhibition studies strengthened the support for a ping‐pong mechanism and allowed evaluation of Ki values for the four substrates. The equilibrium constant evaluated from the kinetic parameters is 40. Additionally, some physical properties relative to the bound coenzyme and the secondary structure were investigated. The results are consistent with a structural relationship between the Escherichia coli enzyme and the mammalian enzyme. The mammalian enzyme has specific kinetic parameters, the determination of which is a prerequisite to analyzing the serine biosynthetic pathway in mammals.