Part of the gene cluster that mediates the biosynthesis of imizoquins A to D, tripeptide-derived alkaloids that serve a protective role against oxidative stress that are essential for normal germination (PubMed:29182847). ImqB is a canonical three-module NRPS that assembles the tripeptide backbone of the imizoquins via condensation of Trp, Tyr, and Leu-derived precursors (PubMed:29182847). N-methylation by imqF and phenol oxidation by imqC, followed by cyclization via the FAD-dependent oxidase imqH carry out the three-step transformation of L-tyrosine into tetrahydroisoquinoline (PubMed:29182847). Importantly, this sequence requires the presence of a free amine in the tyrosine moiety, indicating that isoquinoline formation occurs prior to peptide bond formation (PubMed:29182847). The imidazolidin-4-one ring of imizoquins could form following additional oxidation of the methyl-derived bridgehead carbon by imqH (PubMed:29182847). Lastly, O-methylation by imqG and leucine hydroxylation by imqE complete biosynthesis of the imizoquins (PubMed:29182847). Secondary metabolite biosynthesis. Expression is down-regulated by ralstonins, lipopeptides produced by the plant pathogenic bacteria Ralstonia solanacearum (PubMed:29182847). Expression is positively regulated by the imizoquins cluster-specific transcription regulator imqK (PubMed:29182847).