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 H 2 O 2 via the oxidative‐coupled assay system. ACO activity was assessed spectrophotometrically in the P 20000 g fraction of glucose‐grown (FS 0 ) and n ‐alkane grown cultures (FS alk ), employing acyl‐CoAs of 16 to 24 carbons as substrates. A significant increment in the activity was observed in FS alk as compared to that of controls (FS 0 ) 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‐amino‐1,2,4‐triazole (AT) to prevent H 2 O 2 consumption by endogenous catalase, the lag phase became shorter and disappeared when AT concentrations were raised from 40 to 200 m M , thus enhancing acyl‐CoA oxidation. Enzyme activity reached its maximal value in the presence of 240 μg peroxidase, 0.08% Triton X‐100 and 36 μ M bovine serum albumin. The apparent Km using lignoceroyl as substrate was estimated 2.5 μ 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. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)