Evidence for a complex of three beta-oxidation enzymes in Escherichia coli: induction and localization

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Abstract
The enzymes for .beta.-oxidation of fatty acids in inducible and constitutive strains of E. coli were assayed in soluble and membrane fractions of disrupted cells by using fatty acid and acyl-CoA substrates containing 4 or 16 C atoms in the acyl moieties. Cell fractionation was monitored, using succinic dehydrogenase as a membrane marker and glucose-6-phosphate dehydrogenase as a soluble marker. Acyl-CoA synthetase activity was detected exclusively in the membrane fraction, but acyl-CoA dehydrogenase, 3-hydroxyacyl-CoA dehydrogenase, enoyl-CoA hydratase and 3-ketoacyl-CoA thiolase activities that utilized both C4 and C16 acyl-CoA substrates were isolated from the soluble fraction. 3-Hydroxyacyl-CoA dehydrogenase, enoyl-CoA hydratase and 3-ketoacyl-CoA thiolase activities assayed with C4 and C16 acyl-CoA substrates co-chromatographed on gel filtration and ion-exchange columns and cosedimented in glycerol gradients. These 3 enzyme activities of the fad regulon can apparently be isolated as a multienzyme complex. This complex dissociates in very dilute preparations, but in those preparations where the 3 activities are separated, the fractionated species retain activity with C4 and C16 acyl-CoA substrates.

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