Highly reducing polyketide synthase; part of the gene cluster that mediates the biosynthesis of the lipopeptide antibiotics leucinostatins that show extensive biological activities, including antimalarial, antiviral, antibacterial, antifungal, and antitumor activities, as well as phytotoxic (PubMed:27416025). Leucinostatin A contains nine amino acid residues, including the unusual amino acid 4-methyl-L-proline (MePro), 2-amino-6-hydroxy-4-methyl-8-oxodecanoic acid (AHyMeOA), 3-hydroxyleucine (HyLeu), alpha-aminoisobutyric acid (AIB), beta-Ala, a 4-methylhex-2-enoic acid at the N-terminus as well as a N1,N1-dimethylpropane-1,2-diamine (DPD) at the C-terminus (Probable). The biosynthesis of leucinostatins is probably initiated with the assembly of 4-methylhex-2-enoic acid by a reducing PKS. Two reducing polyketide synthases, lcsB and lcsC, have been identified in the cluster and it is not clear which is the one that assembles 4-methylhex-2-enoic acid since both contain KS, AT, DH, cMT, ER, KR and ACP domains (Probable). The polyketide residue might be transferred to the NRPS lcsA, mediated by two additional enzymes, the acyl-CoA ligase lcsD and the thioesterase lcsE. The linear polyketide carboxylic acid, which is released from PKS, is converted to a CoA thioester by lcsD, and then lcsE hydrolyzes the thiol bond and shuttles the polyketide intermediate to lcsA (Probable). The C domain of the first module catalyzed the condensation of 4-methylhex-2-enoic acid and MePro carried by domain A1, followed by successive condensations of nine amino acids to trigger the elongation of the linear peptide. A5 and A6 domains of lcsA are proposed to incorporate leucine, A2 AHyMeOA, and A3 incorporates HyLeu. A4, A7 and A8 incorporate AIB (Probable). The AHyMeOA in leucinostatin A activated by the A2 might be produced by the second PKS (lcsB or lcsC) present within the cluster (Probable). The MePro is probably produced via leucine cyclization and may originate from a separate pathway, independent of the cluster. Another nonproteinogenic amino acid, beta-Ala, could be produced by an aspartic acid decarboxylase also localized outside of the cluster. Two candidates are VFPBJ_01400 and VFPBJ_10476 (Probable). The final peptide scaffold may be released by the NAD(P)H-dependent thioester reductase (TE) at the C-terminal region of lcsA (Probable). Transamination of the lcsA product by the transaminase lcsP may produce DPD at the C-terminus (Probable). Further hydroxylation steps performed alternatively by the cytochrome P450 monooxygenases lcsI, lcsK andr lcsN then yield the non-methylated leucinostatins precursor. It is also possible that leucines can be hydroxylated prior to their incorporation into the peptide (Probable). Varying extents of methylation then lead to the formation of leucinostatins A and B (Probable). Secondary metabolite biosynthesis. Expression is positively regulated by the leucinostatins biosynthesis cluster-specific transcription regulator lcsF. Multidomain protein; including a ketosynthase (KS) that catalyzes repeated decarboxylative condensation to elongate the polyketide backbone; a malonyl-CoA:ACP transacylase (MAT) that selects and transfers the extender unit malonyl-CoA; a dehydratase (DH) domain that reduces hydroxyl groups to enoyl groups; a methyltransferase (CMeT) domain responsible for the incorporation of methyl groups; an enoylreductase (ER) domain that reduces enoyl groups to alkyl group; a ketoreductase (KR) domain that catalyzes beta-ketoreduction steps; and an acyl-carrier protein (ACP) that serves as the tether of the growing and completed polyketide via its phosphopantetheinyl arm.