Flavin-dependent halogenase malA

UniProtKB accession:  L0E155

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UniProtKB description:  Flavin-dependent halogenase; part of the gene cluster that mediates the biosynthesis of malbrancheamide, a dichlorinated fungal indole alkaloid that belongs to a family of natural products containing a characteristic bicyclo[2.2.2]diazaoctane core (PubMed:23213353, PubMed:31548667, PubMed:28777910). The first step of malbrancheamide biosynthesis involves coupling of L-proline and L-tryptophan by malG, a bimodular NRPS, to produce L-Pro-L-Trp aldehyde through reductive offloading (PubMed:23213353, PubMed:31548667). This compound undergoes spontaneous cyclization and dehydration to give a dienamine which is reverse prenylated at C-2 by malE (PubMed:31548667). The other prenyltransferase present in the cluster, malB, displays modest activity, suggesting that may be a redundant gene in the pathway (PubMed:31548667). Subsequently, a [4+2] Diels-Alder cyclo-addition catalyzed by the bifunctional enzyme malC forms the characteristic bicyclo[2.2.2]diazaoctane ring of premalbrancheamid (PubMed:31548667). Finally, the flavin-dependent halogenase malA catalyzes the iterative dichlorination of the indole ring of premalbrancheamide to yield C-9 monochlorinated malbrancheamide B, C-8 monochlorinated isomalbrancheamide B, and dichlorinated malbrancheamide (PubMed:31548667, PubMed:28777910). MalA is also able to brominate premalbrancheamide at C-9 to yield malbrancheamide C, and, to a lesser extend, at C-8 to yield isomalbrancheamide C (PubMed:28777910). Finally, malA can brominate C-9 monochlorinated malbrancheamide B at C-8 to yield malbrancheamide D, or C-8 monochlorinated isomalbrancheamide B at C-9 to produce isomalbrancheamide D (PubMed:28777910).