ABSTRACT
An NADPH-dependent oxidoreductase has been extracted from the mycelium of the fungus Mucor Javanicus (Wehmer) and enriched 1000-fold with respect to the protein contained in the crude extract after centrifugation at 2600 X g. The molecular weight of the enzyme was estimated by gel filtration to be about 100 000; electrophoresis under dissociating conditions indicates four subunits of molecular weight about 28 000. Data on stability and activity of the enzyme as a function of pH and temperature are reported. From a kinetic study and product analysis of the reduction of the two enantiomeric trans-1-decalones and also from a kinetic study of the oxidation of the two diastereomeric pairs of trans-1-decalols it follows that the enzymes is an e-Si oxidoreductase (according to the nomenclature proposed by Dutler et al., Eur. J. Biochem. 22 [1971]203-212 and Prelog and Helmchen, Helv. Chim. Acta, 55 [1972] 2581-2598). This classification is amply confirmed by the kinetic behaviour of a large number of alicyclic substrates. Using (4-2HSi-labelled coenzyme to reduce (9S)-trans-1,4-decalindione, it was shown that the enzyme is HSi (= HS = HB)-stereospecific with respect to the coenzyme. It is demonstrated that the oxidoreductase from Mucor javanicus can be used for the preparation of optically pure chiral alcohols and ketones. In the following paper evidence is presented that the natural substrate of the enzyme is dihydroxyacetone.