Sam5, a Coumarate 3-Hydroxylase from Saccharothrix espanaensis: New Insight into the Piceatannol Production as a Resveratrol 3’-Hydroxylase.

Piceatannol is an important natural stilbene, which show a broad range of biological activities of medicinal interest. In recent studies, the Sam5 enzyme from Saccharothrix espanaensis was found to catalyze the conversion of p-coumaric acid to caffeic acid as a coumarate 3-hydroxylase (C3H). In this report, we show that purified recombinant Sam5 enzyme exhibited 5.7-fold higher resveratrol ortho-hydroxylation (resveratrol 3’-hydroxylase; R3’H) activity to produce piceatannol compared to the C3H activity. The substrate saturation curve of the Sam5 enzyme for resveratrol is far superior to that for p-coumaric acid. In addition, we constructed a biological platform to produce piceatannol by adding a sam5 gene in a resveratrol artificial biosynthetic pathway that was already made. According to the results, piceatannol production as high as 31.5 ± 6.3 mg/L was achieved.