Affiliation:
1. Department of Biochemistry, University of Aberdeen, Marischal College, Aberdeen AB9 1AS, U.K.
Abstract
The behaviour of various C19 and C18 steroids as substrates for crystalline preparations of cortisone reductase (EC 1.1.1.53) is described. 3α(Axial,3R)-, 3α(equatorial,3R)- and 3β(axial,3S)-hydroxy steroid–NAD oxidoreductase activities are demonstrated. Four pairs of the substrates differed only in the shape of the a/b ring junction, three pairs differed only in substitution at C-10, and four pairs differed only in substitution in ring d. The shape of the substrate molecule and certain substituents (e.g. 10β-methyl, 17β-hydroxy, 16-oxo or 17-oxo) altered substrate behaviour, but steroids differing considerably in shape nevertheless acted as substrates, suggesting the possibility of a large or flexible binding site. Km values varied about 10-fold, many being approx. 140μm. Vmax. values covered a greater range (about 200-fold) and the good substrates had high Vmax. values rather than low Km values.
Subject
Cell Biology,Molecular Biology,Biochemistry
Cited by
18 articles.
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