Recombinant 10-formyltetrahydrofolate dehydrogenase catalyses both dehydrogenase and hydrolase reactions utilizing the synthetic substrate 10-formyl-5,8-dideazafolate.

Krupenko SA, Wagner C, Cook RJ
Biochem J. 1995 306 ( Pt 3): 651-5

PMID: 7702556 · PMCID: PMC1136571 · DOI:10.1042/bj3060651

10-Formyltetrahydrofolate dehydrogenase (EC 1.5.1.6) is a bifunctional enzyme, displaying both NADP(+)-dependent dehydrogenase activity for the formation of tetrahydrofolate and CO2, and NADP(+)-independent hydrolase activity for the formation of tetrahydrofolate and formate. A previous report [Case, Kaisaki and Steele (1988) J. Biol. Chem. 263, 1024-1027] claimed that dehydrogenase and hydrolase activities were products of separate cytosolic and mitochondrial forms of this enzyme. Here we report that recombinant 10-formyltetrahydrofolate dehydrogenase carries out both enzymic reactions, proving that a product of a single gene, i.e. one protein, not two, has both activities. The stable synthetic analogue 10-formyl-5,8-dideazafolate can substitute for the labile natural substrate, 10-formyltetrahydrofolate, in both reactions. This was shown with both native and recombinant rat liver enzyme. The Km values for 10-formyl-5,8-dideazafolate were half of those for 10-formyltetrahydrofolate in both the dehydrogenase and hydrolytic reactions. The Vmax, values were similar for both substrates. Both dehydrogenase and hydrolase reactions were dependent on the presence of 2-mercaptoethanol. The pH optima were 7.8 and 5.6 for the dehydrogenase and hydrolase reactions respectively, consistent with the presence of two active sites in the enzyme.

MeSH Terms (8)

Enzyme Activation Folic Acid Hydrolases Mercaptoethanol Oxidoreductases Oxidoreductases Acting on CH-NH Group Donors Recombinant Fusion Proteins Substrate Specificity

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