AMP-dependent ligase; part of the gene cluster that mediates the biosynthesis of verlamelin, a lipopeptide that exhibits antifungal activity against plant pathogenic fungi (PubMed:24848421). Verlamelin is a cyclic hexadepsipeptide and is bridged by ester bonding between a 5-hydroxytetradecanoic acid moiety and a carboxyl group on the terminal Val of amide-bonded tetradecanoyl-hexapeptide D-allo-Thr-D-Ala-L-Pro-L-Gln-D-Tyr-L-Val (PubMed:24848421). VlmA and vlmB are altogether regarded as essential components in the biosynthesis of 5-hydroxytetradecanoic acid (PubMed:24848421). VlmA catalyzes the hydroxylation at position C5 of tetradecanoic acid produced in primary metabolism, while the precise function of vlmB still remains to be solved (PubMed:24848421). To be loaded onto the waiting NRPS, 5-hydroxytetradecanoic acid is activated in the form of acyladenylate by the AMP-dependent ligase vlmC (PubMed:24848421). VlmS seems to accept the fatty-acyl intermediate onto the initial module to further elongate amino acid residues by the downstream modules (PubMed:24848421). In addition, in the last module at its C-terminus, vlmS contains a surplus condensation (C) domain that may be involved in cyclization, the last step to form verlamelin (PubMed:24848421).