Coenzyme Activity of NAD Analogs for 3-Isopropylmalate Dehydrogenase from Thermus thermophilus HB8

Abstract

  In order to elucidate the enzyme-substrate-cofactor interaction in 3-isopropylmalate dehydrogenase, the coenzyme activity of NAD analogs which have a 3-substituted pyridine ring was examined. Analogs 3-5 showed diminished k_cat values compared with those of NAD⁺, whereas thiocarboxamide 2 was almost as equally active as NAD⁺. This suggests that the NH₂ functionality of NAD⁺ is more important for the catalysis of IPMDH than a carbonyl group.