Steroids and steroidases. VI. On the C-17 specificity of the Δ5-3-ketoisomerase of Pseudomonas testosteroni and evidence for substrate micelle formation

Abstract

Studies on the acid-, base-, and enzyme-catalyzed isomerizations of several variously C-17 substituted Δ⁵-3-ketosteroids have indicated micellar aggregation of relatively non polar substrates in the dilute aqueous methanol assay solvent to be an important consideration when evaluating specificity data. Further evidence that the isomerase is sensitive to the presence of 17α-substituents in its substrates has been obtained and the probability that tyrosine is the acid catalytic group at the active center is discussed.