Substrate specificity of two cytochrome P450 monooxygenases involved in lankamycin biosynthesis

Biocatalytic role of cytochrome P450s to produce antibiotics: A review

Cytochrome P450s belong to a family of heme-binding monooxygenases, which catalyze regio- and stereospecific functionalisation of C-H, C-C, and C-N bonds, including heteroatom oxidation, oxidative C-C bond cleavages, and nitrene transfer. P450s are considered useful biocatalysts for the production of pharmaceutical products, fine chemicals, and bioremediating agents. Despite having tremendous biotechnological potential, being heme-monooxygenases, P450s require either autologous or heterologous redox partner(s) to perform chemical transformations. Randomly distributed P450s throughout a bacterial genome and devoid of particular redox partners in natural products biosynthetic gene clusters (BGCs) showed an extra challenge to reveal their pharmaceutical potential. However, continuous efforts have been made to understand their involvement in antibiotic biosynthesis and their modification, and this review focused on such BGCs. Here, particularly, we have discussed the role of P450s involved in the production of macrolides and aminocoumarin antibiotics, nonribosomal peptide (NRPSs) antibiotics, ribosomally synthesized and post-translationally modified peptide (RiPPs) antibiotics, and others. Several reactions catalyzed by P450s, as well as the role of their redox partners involved in the BGCs of various antibiotics and their derivatives, have been primarily addressed in this review, which would be useful in further exploration of P450s for the biosynthesis of new therapeutics.

Isolation of Hydrazide-alkenes with Different Amino Acid Origins from an Azoxy-alkene-Producing Mutant of Streptomyces rochei 7434AN4

A triple mutant (strain KA57) of Streptomyces rochei 7434AN4 produces an azoxy-alkene compound, KA57A, which was not detected in a parent strain or other single and double mutants. This strain accumulated several additional minor components, whose structures were elucidated. HPLC analysis of strain KA57 indicated the presence of two UV active components (KA57D1 and KA57D2) as minor components. They exhibited a maximum UV absorbance at 218 nm, whereas a UV absorbance of azoxy-alkene KA57A was detected at 236 nm, suggesting that both KA57D1 and KA57D2 contain a different chromophore from KA57A. KA57D1 has a molecular formula of C12H22N2O2, and NMR analysis revealed KA57D1 is a novel hydrazide-alkene compound, (Z)-N-acetyl-N'-(hex-1-en-1-yl)isobutylhydrazide. Labeling studies indicated that nitrogen Nβ of KA57D1 is derived from l-glutamic acid, and the isobutylamide unit (C-1 to C-3, 2-Me, and Nα) originates from valine. KA57D2 has a molecular formula of C13H24N2O2, and its structure was determined to be (Z)-N-acetyl-N'-(hex-1-en-1-yl)-2-methylbutanehydrazide, in which a 2-methylbutanamide unit was shown to originate from isoleucine. Different biogenesis of the Nα atom (l-serine for KA57A, l-valine for KA57D1, and l-isoleucine for KA57D2) indicates the relaxed substrate recognition for nitrogen-nitrogen bond formation in the biosyntheses of KA57A, KA57D1, and KA57D2.

Accumulation of lankamycin derivative with a branched-chain sugar from a blocked mutant of chalcose biosynthesis in Streptomyces rochei 7434AN4

Lankamycin, a macrolide antibiotic produced by Streptomyces rochei 7434AN4, exhibits a moderate antimicrobial activity and acts as a synergistic pair with carbocyclic antibiotic lankacidin C by binding to the ribosome exit tunnel. Its biosynthetic gene (lkm) cluster (orf24-orf53) is located on the largest plasmid pSLA2-L (210,614 bp). Our group possesses a variety of lankamycin derivatives and macrolide-modification enzymes including P450 enzymes and glycosyltransferases, which may lead to expand the chemical library of bioactive macrolides. Here we constructed a mutant of a 3-ketoreductase gene lkmCVI (orf42) involved in d-chalcose biosynthesis, and its metabolite was isolated and structure-elucidated. Accumulation of novel lankamycin derivative harboring a branched-chain deoxysugar, 5-O-(4',6'-dideoxy-3'-C-acetyl-d-ribo-hexopyranosyl)-3-O-(4″-O-acetyl-l-arcanosyl)-lankanolide, indicated that LkmCVI acts as a gate keeper enzyme for d-chalcose synthesis in lankamycin biosynthesis.