Figure 2.

Alternate routes for the incorporation of β-hydroxy amino acids in NRPS-mediated peptide biosynthesis. (A) Hydroxylation of the Tyr₆ residue by a diiron monooxygenase in type IV GPA biosynthesis occurs during peptide assembly with the residue covalently attached to module 6 of the NRPS. (B,C) Modification of amino acids by diiron monooxygenases during peptide assembly in bleomycin (His₈) and lysobactin (Phe₃, Leu₄, and Asn₁₀) biosynthesis. (D) Multiple oxidation of different amino acids in the biosynthesis of skyllamycin (Phe₅, OMe-Tyr₇, Leu₁₁) by a cytochrome P450 monooxygenase. (E) Provision of Bht precursors for the NRPS assembly lines that form type I–III GPAs utilizes a P450-mediated hydroxylation of Tyr on a separate, dedicated NRPS module. (F) Activity of the diiron monooxygenase CmlA toward PCP-bound 4-aminophenylalanine in chloramphenicol biosynthesis.