Hydroxylation of diverse flavonoids by CYP450 BM3 variants: biosynthesis of eriodictyol from naringenin in whole cells and its biological activities

BACKGROUND Cytochrome P450 monooxygenase constitutes a significant group of oxidative enzymes that can introduce an oxygen atom in a high regio- and stereo-selectivity mode. We used the Bacillus megaterium cytochrome P450 BM3 (CYP450 BM3) and its variants namely mutant 13 (M13) and mutant 15 (M15) for the hydroxylation of diverse class of flavonoids. RESULTS Among 20 flavonoids, maximum seven flavonoids were hydroxylated by the variants while none of these molecules were accepted by CYP450 BM3 in in vitro reaction. Moreover, M13 exhibited higher conversion of substrates than M15 and CYP450 BM3 enzymes. We found that M13 carried out regiospecific 3'-hydroxylation reaction of naringenin with the highest conversion among all the tested flavonoids. The apparent K m and k cat values of M13 for naringenin were 446 µM and 1.955 s(-1), respectively. In whole-cell biotransformation experiment with 100 µM of naringenin in M9 minimal medium with 2 % glucose in shake flask culture, M13 showed 2.14- and 13.96-folds higher conversion yield in comparison with M15 (16.11 %) and wild type (2.47 %). The yield of eriodictyol was 46.95 µM [~40.7 mg (13.5 mg/L)] in a 3-L volume lab scale fermentor at 48 h in the same medium exhibiting approximately 49.81 % conversion of the substrate. In addition, eriodictyol exhibited higher antibacterial and anticancer potential than naringenin, flavanone and hesperetin. CONCLUSIONS We elucidated that eriodictyol being produced from naringenin using recombinant CYP450 BM3 and its variants from B. megaterium, which shows an approach for the production of important hydroxylated compounds of various polyphenols that may span pharmaceutical industries.