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Title
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[Isolation and properties of phosphoribosyl-aminoimidazole-succinocarboxyamide-synthestase from Saccharomyces cerevisiae yeasts].
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Authors
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K.V.Ostanin,
V.V.Alenin,
V.D.Domkin,
M.N.Smirnov.
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Ref.
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Biokhimiia, 1989,
54,
1265-1273.
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PubMed id
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Abstract
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An isolation procedure for phosphoribosyl succinocarboxamideaminoimidazole
synthetase (SAICAR synthetase) (EC 6.3.2.6) has been developed. Pure SAICAR
synthetase was found to be a monomeric protein with the apparent molecular
weight of 36 kDa. The Michaelis constant for the three substrates of the
reaction are 1.6 microM for CAIR, 14 microM for ATP and 960 microM for aspartic
acid. The structural analogs of CAIR, 5-aminoimidazole ribotide and
5-aminoimidazole-4-carboxamide ribotide, act as competitive inhibitors of SAICAR
synthetase. GTP and 2'-dATP can substitute for ATP in the reaction, while CTP
and UTP inhibit the enzyme. No structural analogs of the aspartic acid were
found to have affinity for SAICAR synthetase. The optimal reaction conditions
for the enzyme were established to be at pH 8.0 and magnesium chloride
concentration around 5 mM.
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