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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 × g. The molecular weight of the enzyme was estimated by gel filtration to be about 100000; electrophoresis under dissociating conditions indicates four subunits of molecular weight about 28000. 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 enzyme is an e-Si oxidoreductase (according to the nomenclature proposed by Duller 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 (4-2 Hsi-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. [ABSTRACT FROM AUTHOR]

An enzyme, exhibiting NAIDPH-dependent oxidoreductase activity towards alicyclic ketones has been extracted from pig liver and purified 122-fold with respect to the protein contained in the crude extract after centrifugation at 54000×g. General properties, ultraviolet spectrum, stability, kinetic constants (V and Km) for NADPH and for typical substrates are reported. The molecular weight of the enzyme was estimated at 500000 by gel-filtration. The enzyme is HS(HB)-specific with respect to coenzyme. Alicyclic ketones can be conveniently used to measure the activity at all stages of purification. The topography of the active site responsible for oxidoredutase activity has been investigated by use of rigid alicyclic ketones such as trans-decal-1-ones as probes. In the accompanying paper it is shown (1) that the biological function of the whole enzyme complex is that of a fatty acid synthetase and (2) that the oxidoreductase activity can be ascribed to its 3-oxoacyl-acyl-carrier protein reductase component. [ABSTRACT FROM AUTHOR]