Abstract
3α,7α,12α-Trihydroxy-5β-cholestan-26-al dehydrogenase (3 α,7 α,12 α-trihydroxy-5β-cholestan-26-al + NAD + + H 2O → 3α,7α,12α-trihydroxy-5β-cholestan-26-oic acid + NADH + H +) in a soluble fraction of horse liver was studied. 1. 1. Horse liver 3α,7α,12α-trihydroxy-5β-cholestan-26-al dehydrogenase consists of two components, the major one of which was purified about 70-fold by (NH 4) 2SO 4 fractionation, gel filtration, ion-exchange column chromatography and hydroxylapatite column chromatography. 2. 2. 3α,7α,12α-trihydroxy-5β-cholestan-26-al dehydrogenase was always accompanied by liver aldehyde:NAD oxidoreductase (EC 1.2.1.3) activity, and the ratio of these two enzyme activities was not altered by purification. 3. 3. Both 3α,7α,12α-trihydroxy-5β-cholestan-26-al dehydrogenase and horse liver aldehyde:NAD + oxidoreductase were reduced to a similar extent on inactivation of the purified enzyme by heating or by incubation with p-chloromercuribenzoate. 4. 4. The K m value for NAD + of 3α,7α,12α-trihydroxy-5β-cholestan-26-al dehydrogenase was found to be roughly equal to that of liver aldehyde:NAD + oxidoreductase. 5. 5. The possibility was discussed that both 3α,7α,12α-trihydroxy-5β-cholestan-26-al dehydrogenase and liver aldehyde:NAD + oxidoreductase activities may be due to a single protein.
Published Version
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