Hydroxylation of deoxycorticosterone by Bacillus cereus, strain T

• Published in: Archives of biochemistry and biophysics Vol. 114; no. 1; pp. 166 - 177
• Main Authors: Wilson, John E., Ober, R.E., Vestling, C.S.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.04.1966
• Subjects: Bacillus cereus - metabolism; Carbon Monoxide; Cyanides; Desoxycorticosterone - metabolism; Electron Transport Complex IV - metabolism; Methylene Blue; Mixed Function Oxygenases - metabolism
• DOI: 10.1016/0003-9861(66)90318-3
• ISSN: 0003-9861

Deoxycorticosterone (DOC) is monohydroxylated by Bacillus cereus, strain T, to give the 6β-, 14α-, 15α-, and 15β-hydroxy isomers in the approximate ratios of 2:3:2:2. No evidence for metabolism of DOC beyond the monohydroxylated stage has been found. The steroid hydroxylating system is not dependent on the presence of steroid in the growth medium for either its appearance or its level of activity. The activity increases approximately tenfold during the late logarithmic growth phase of the organism. Increased levels of the tricarboxylic acid cycle enzymes and of a particulate electron transport system also are formed during this period of growth. The steroid hydroxylation reaction is subject to light-reversible inhibition by carbon monoxide. The photochemical action spectrum of the reaction shows peaks in the region of 430 and 415 mμ. The peaks are attributed to the carbon monoxide complexes of cytochrome oxidase (428 mμ) and of a second, unidentified pigment (414 mμ). These are the only two carbon monoxide complexes detected in the cells by the difference spectrum technique. The hydroxylation reaction is stimulated by cyanide and inhibited by methylene blue. The possibility that steroid hydroxylation represents an “accidental” result of a terminal oxidase reaction is considered as an explanation for the widespread steroid hydroxylating activity of bacteria, a reaction which appears to have little metabolic significance in many of these organisms.