Selective hydroxylation of highly branched fatty acids and their derivatives by CYP102A1 from Bacillus megaterium

Abstract

Highly branched fatty acids, representing the main component of the preen gland wax of the domestic goose, and their derivatives are promising chiral precursors for the synthesis of macrolid antibiotics. The key step in utilisation of these compounds is the regioselective hydroxylation, which can not be done in a classical chemical approach. Three P450 monooxygenases CYP102A1, CYP102A2 and CYP102A3, demonstrating high turnover numbers in hydroxylation of iso and anteiso fatty acids (>400 min-1), were tested for their activity towards these substrates. CYP102A1 from Bacillus megaterium as well as its A74G F87V L188Q triple mutant hydroxylate a variety of these substrates with high activity and regioselectivity. In all cases the triple mutant showed much higher activities than the wild type enzyme. The binding constants, determined for CYP102A1 wild type and the triple mutant were >200 µM and ~23 µM, respectively, when tetramethyl nonanol was used as substrate. The data derived from binding analysis supports the differences in activity found for the CYP102A1 wild type and the triple mutant. Surprisingly the CYP102A2 and CYP102A3 from Bacillus subtilis did not show activity at all. Substrate binding spectra, recorded to investigate substrate accessibility to the enzyme’s active site, revealed that the substrates either could not access the active site of the Bacillus subtilis monooxygenases, or did not reach the heme proximity.