3α-Hydroxysteroid dehydrogenase activity in the cytosolic fractions of human placenta, kidney and liver

Gyapong, Tony Emmanuel (1986) 3α-Hydroxysteroid dehydrogenase activity in the cytosolic fractions of human placenta, kidney and liver. Masters thesis, Memorial University of Newfoundland.

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Abstract

Although the major metabolites of 3-ketosteroids voided in human urine are 3α-hydroxysteroids or their derivatives, there has been very little published work on the purification and characterization of the human 3α-hydroxysteroid dehydrogenases which must be involved in their genesis. -- The presence of the 3α-hydroxysteroid dehydrogenases in human liver, kidney and placenta has been demonstated by incubation of extracts of these tissues with 17α-methyl-5α-androstane-3α,17β-diol which was converted to the 3-ketone. This was identified by thin layer chromatography and by high performance liquid chromatography and by further characterization after sodium borohydride reduction of the 3-ketone to the 3β-alcohol. -- The NAD-dependent liver cytosol enzyme activity found in the 40-60% ammonium sulphate precipitate has been partially purified using ion-exchange and gel filtration chromatography. The 3α-HSD activity appears to reside in a number of isozymes separable by carboxymethyl-cellulose chromatography one is tentatively identified as being a human liver ADH, β1β1 which was shown by iso-electric focussing to have a pI between 9 and 10. 4-Methyl pyrazole was found to inhibit the ethanol dehydrogenase activity but not the 3α-HSD activity of these isozymes. -- A two-fold ratio of 3α- : 3β-HSD activity was observed in the human kidney cytosol but the activity in the microsomal fraction was entirely due to 3β-HSD with only a trace of 3α-HSD activity. The 3α-HSD activity found in the cytosolic fraction of the human placenta was very unstable.

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