On the mechanism of hydrogen transfer by nicotinamide coenzymes and alcohol dehydrogenase

Abstract

The oxidation of exo-bicyclo[4.1.0]heptan-7-ylmethanol and of bicyclo[4.1.0]heptan-2-ol and the reduction of the corresponding carbonyl compounds by horse liver alcohol dehydrogenase (E.C.1.1.1.1) occur without cleavage of the three-membered ring. Reactions of these substrates with hydride donating and abstracting reagents also proceed with retention of the small ring whereas radical reactions lead to cleavage of the cyclopropane ring. These results, together with kinetic studies on the rates of ring opening of cyclopropylmethyl silyl ethers by e.s.r. spectroscopy suggest that the enzyme-catalysed reaction takes place through transfer of hydrogen as hydride.