Acyl-CoA oxidase activity from Beauveria bassiana, an entomopathogenic fungus

Beauveria bassiana produces acyl-Co oxidase (ACO) in the P-20000 g fraction of glucose and alkane-grown cultures that catalyze the oxidation of acyl-CoAs of different chain length. The activity was measured indirectly over the formation of H2O2 via the oxidative-coupled assay system. ACO activity was assessed spectrophotometrically in the P-20000 g fraction of glucose-grown (FS0) and n-alkane grown cultures (FSalk), employing acyl-CoAs of 16 to 24 carbons as substrates. A significant increment in the activity was observed in FSalk as compared to that of controls (FS0) in all conditions tested. Tetracosane-grown cultures showed the highest activity with lignoceroyl-CoA. The reaction conditions were optimized employing lignoceroyl-CoA as substrate. A variable lag phase was observed when the activity was measured as a function of time. In the presence of 3-anuno-1,2,4-triazole (AT) to prevent H2O2 consumption by endogenous catalase, the lag phase became shorter and disappeared when AT concentrations were raised from 40 to 200 mm, thus enhancing acyl-CoA oxidation. Enzyme activity reached its maximal value in the presence of 240 mu g peroxidase, 0.08% Triton X-100 and 36 pm bovine serum albumin. The apparent Km using lignoceroyl as substrate was estimated 2.5 mu m. ACO showed high activity and stability between 30 and 40 C, as well as between 7.0 and 9.0 pH, for 120 min, being 7.0 the optimum pH.