Studies of 3-oxo steroid Δ 1-oxydo reductase of Arthrobacter simplex

Abstract

An active cell-free preparation from Arthrobacter simplex has been obtained by a procedure involving the culture and induction by steroids of the bacteria, spheroplast formation by lysozyme, nucleic acid elimination by streptomycin and ammonium sulfate precipitation. The 3-oxo Δ 4-steroid Δ 1-oxydo reductase activity is found in the small particle fraction. There is no correlation between enzyme biosynthesis and growth. Studies indicate that the concentration of cortisol for inducing half maximally the enzyme (maximum enzymatic activity per cell) is approx 1 × 10 −5 M. A survey of the substrate characteristics of several steroids (using a cell-free preparation) shows an important contribution of the middle part of the α-face in the enzyme substrate interaction. Dicortinone is a powerful non competitive, and 5 α-androstane-3, 17-dione a competitive inhibitor of Δ 1-oxydo reductase.