A reinvestigation of the mechanism of delta 5-3-ketosteroid isomerase from bovine adrenal glands.
The mechanism of the isomerization of androst-5-ene 3,17-dione by the isomerase of bovine adrenals has been reinvestigated using the methodology previously developed for the study of the bacterial enzyme of Pseudomonas testosteroni. However, owing to the lower activity of the mammalian enzyme, competitive non-enzymic reaction cannot be neglected. It has been shown that even in the absence of spontaneous isomerization, epimerization and exchange of the label on C4 takes place in the buffer. This prevents any quantitative discussion of the course of the reaction. It is however possible to conclude that the mechanism we have proposed for the bacterial enzyme that is, besides the classical 4 beta leads to 6 beta transfer and exchange with the medium, a competitive abstraction of the 4 alpha proton, accounts for the data obtained with the mammalian microsomes.
D000311:Adrenal Glands / Q000201:enzymology*; D000735:Androstenedione / Q000378:metabolism; D000818:Animals; D002417:Cattle; D003903:Deuterium; D006863:Hydrogen-Ion Concentration; D007535:Isomerases / Q000378:metabolism*; D008861:Microsomes / Q000201:enzymology; D011549:Pseudomonas / Q000201:enzymology; D013251:Steroid Isomerases / Q000378:metabolism*
D000735:Androstenedione; D003903:Deuterium; D007535:Isomerases; D013251:Steroid Isomerases; C022660:steroid delta-isomerase