- Characterization of the acyl-CoA oxidase in Beauveria bassiana

ALCONADA T. AND JUÁREZ, M. PATRICIA

Pinamar

Congreso; XLI Reunión Anual de la Sociedad Argentina de Investigaciones Bioquímicas y Biología Molecular; 2005

SAIB

CHARACTERIZATION OF THE ACYL-COA OXIDASE IN BEAUVERIA BASSIANA. Alconada, Teresa and Juárez, M. Patricia. Instituto de Investigaciones Bioquímicas de La Plata (CONICET-UNLP), Facultad de Ciencias Médicas, calles 60 y 120 (1900) La Plata, Argentina e-mail: talconada@mdht.com.ar   The entomophatogenic fungi Beauveria bassiana has the ability to metabolize hydrocarbons, characteristic components of the external lipid layer of the insect cuticle. Alkane-growth induction enhances fungal  ability to kill its insect host. After the  initial oxidation steps [hydrocarbon ® alcohol ® very long chain fatty acid (VLCFA)], the first enzyme involved in VLCFA oxidation in peroxisomes is the acyl-CoA oxidase (ACO). ACO activity was measured by spectrophotometry  in the P20000g fraction of glucose-grown (FS0) and n-alkane grown cultures (FSalk) employing acyl-CoAs of 18 to 24 carbons as substrates. A significant increment in the activity was observed in FSalk as compared to that of  controls (FS0). 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 H2O2 consumption by endogenous catalase, the lag phase became shorter and disappeared when AT concentratios was raised from 40 to 200 mM, thus enhancing acyl-CoA oxidation. Enzyme activity was maximal on the presence of 240 ug peroxidase, 0.08 % Triton X-100 and 36 mM BSA. The apparent Km for lignoceroy CoA was 2.5 mM, the  pH optimum was 7. The enzyme was fully stable after 2- h preincubation at pH 7-10.