Biosynthesis of acaterin: Mechanism of the reaction catalyzed by dehydroacaterin reductase

Dehydroacaterin reductase is an enzyme which catalyzes the final step of acaterin biosynthesis, that is, the reduction of the C-4/C-5 double bond of dehydroacaterin. The mechanism of the reduction was investigated with a cell-free preparation obtained from the acaterin-producing microorganism, Pseudomonas sp. A 92. Incubation of dehydroacaterin in the presence of [4,4- 2H 2]NADPH or D 2O followed by 2H NMR analysis of the resulting acaterin revealed that the deuterium atom from NADPH was incorporated into the C-5 position of acaterin, while the deuterium atom from D 2O was introduced into the C-4 position. It was further demonstrated that the pro- R hydrogen at C-4 of NADPH was stereospecifically utilized in this reduction.