Characterization of the P450 Monooxygenase LobP1 as C-32 Hydroxylase in Lobophorin Biosynthesis

Lobophorins (LOBs) belong to a large family of spirotetronate antibiotics with antibacterial and antitumor activities. In this study, we demonstrated the function of LobP1, a P450 monooxygenase encoded in the LOB biosynthetic gene cluster, by in vivo deletion and in vitro biochemical assays. The disruption of lobP1 led to the isolation of three new LOBs derivatives (3‒5) and three known ones (6‒8) without the hydroxyl group at C-32. LobP1 was shown to have relatively broad substrate scope. Determing the kinetic parameters of LobP1 towards different substrates revealed that LobP1 preferred substrate with a nitrosugar. The major product LOB E (6) from the ∆lobP1 mutant displayed better cytotoxic activities against several cancer cell lines than LOB B, the C-32 hydroxlated counterpart.