The catalytic characteristics of NocB in nocathiacin biosynthesis from Nocardia sp. ATCC 202099

Abstract

Nosiheptide and nocathiacin are thiopeptides within the same series with high similarity from chemical structure to organization of the biosynthetic gene cluster. Previously, NosB, a cytochrome P450-like enzyme, was demonstrated to be responsible for the hydroxylation of Glu-6 during nosiheptide maturation. Based on 64% amino acid sequence identity, NocB from Nocardia sp. ATCC 202099 is expected to exhibit a similar catalytic function to NosB. After replacing nosB by nocB in nosiheptide-producing Streptomyces actuosus ATCC 25421, NocB was proved to be a cytochrome P450-like monooxygenase responsible for the hydroxylation of Glu-6 at the γ-position in the biosyntheses of both nosiheptide and nocathiacin. Enzyme kinetics and structural difference between nosiheptide and nocathiacin further revealed that NocB is less active than NosB towards unglycosylated intermediate 3 containing a bicyclic core structure.