Thymidylate Synthase, Dihydrofolate Reductase, Folyl Binder, 10-Formyl-H₄PteGlu Synthetase, 5,10-Methenyl-H₄PteGlu Cyclohydrolase and 5,10-Methylene-H₄PteGlu Dehydrogenase Derived from Cells of Human Origin

Summary

In the past few years we have been engaged in studying several folate cofactor requiring enzymes derived from human cells; namely thymidylate synthase, dihydrofolate reductase, folyl binder, 10-formyl-H₄PteGlu synthetase, 5,10-methenyl-H₄PteGlu cyclohydrolase and 5,10-methylene-H₄PteGlu dehydrogenase. These have been purified and several properties have been examined, in particular the interactions with folyl-polyglutamate forms as substrates and inhibitors. Folylpolyglutamates are better substrates for thymidylate synthase, 10-formyl-H₄PteGlu synthetase, and 5,10-methylene-H₄PteGlu dehydrogenase when NADP is lower than 30 μM, whereas dihydrofolate reductase and membrane associated folyl binder do not distinguish between folylmono- and polyglutamates. Analog studies with thymidylate synthase suggest that there are two types of folate binding sites and this led us to propose a model for the subunit association.

Supported by Grant CA 27364 from NCI, USPHS.

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