Functional characterization of alcohol oxidases from Aspergillus terreus MTCC 6324

Abstract

Short chain alcohol oxidase (SCAO), long chain alcohol oxidase (LCAO), secondary alcohol oxidase (SAO), and aryl alcohol oxidase (AAO) activities were localized in the microsome of Aspergillus terreus during growth of the fungi on n-hexadecane. Zymogram analysis of the microsomes of n-hexadecane-grown cells in polyacrylamide gel electrophoresis showed distinct bands, H4, H3, H2, and H1, in a sequence of their molecular weight (Mr) from high to low. The Mr of the isozymes corresponding to the bands H4, H3, and H2 were close to each other and were higher than 272 kDa. While, the Mr of the isozyme H1 was found to be approximately 48 kDa. H1 gave activity only as SCAO. Although the substrates for other bands were varied, strong (S), medium (M), and weak (W) activity for the bands were as follows: H2: SAO (S), AAO (S), LCAO (M), SCAO (S); H3: LCAO (S), SCAO (S); H4: SCAO (S), LCAO (W), SAO (W). The pH and temperature optima of these isozymes were found to be 8.5+/-0.5 and 30+/-1 degrees C, respectively. The stability of the isozymes was drastically decreased beyond 30 degrees C. The SAO showed 33% enantiomeric excess for the R(-)2-octanol over S(+)2-octanol, which may be correlated with the lower Michaelis-Menten constant (K (M)) values of the enzyme for the R(-)2-octanol than the S(+)2-octanol. The fluorescence emission spectra of the chromatographically purified SCAO at 443 nm excitation were similar to that obtained with authentic flavin adenine dinucleotide.