No abstract

No abstract

No abstract

An NADPH-dependent oxidoreductase has been extracted from the mycelium of the fungus Mucorjavanicus (Wehmer) and enriched 1000-fold with respect to the protein contained in the crude extract after centrifugation at 260Uxg. 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-I-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 Dutler et id., Eur. J. Bioclzem. 22 [1971] 203 -21 2 and Prelog and Helmchen, Helv. Clzim. 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-l,4-decalindione, it was shown that the enzyme is Hsi ( = Hs = HH)-stereospecific with respect to the coenzyme. It is demonstrated that the oxidoreductase from Mucor javunicus 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.In the course of work carried out in our laboratory on the stereochemistry of enzyme-catalyzed oxidoreductions [ 1 -41 a new NADPH-dependent oxidoreductase was isolated from the fungus Mucor ,jawnicus (Wehmer). The enzyme was active towards several aliphatic and alicyclic ketones and the corresponding alcohols. The isolation of dihydroxyacetone from the mycelium extract and the finding that it is a highly active substrate, strongly suggested that the enzyme is a dihydroxyacetone reductase. Evidence in favour of this assumption is presented in the following paper [5].Preliminary experiments with a few alicyclic ketones had shown that the new enzyme transfers hydrogen exclusively to the Si face of the carbonyl. The steric course of hydrogen transfer is thus opposite to that previously reported for reductions catalyzed by other similar oxidoreductases, all of which transfer hydrogen to the Re face [4-71. It was therefore of interest to establish the steric course of the reactions catalyzed by the Mucor enzyme for rigid substrates such as trans-I -decalones and trans-I-decalols. Kinetic ~-Ahh,o~ia/ion. NMR, nuclear magnetic resonance. E 1 1~~7 7 1~.

Coll(salen)t derivatives whose ethanediyl moiety carries an o-alkenyl side chain react with oxygen and methanol or ethanol t o give, via interaction between intermediate Colll species and the pendant olefin, alkylated products with a P-alkoxy substituted carbon bridge between cobalt and the equatorial ligand; the corresponding intermolecular reaction between Coll(salen) and hex-I-ene does not take place.