Nonribisomal peptide synthase; 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). 2 ATP + L-proline + L-tryptophan + NADPH = (S)-3-(indol-3-ylmethyl)-6,7,8,8a-tetrahydropyrrolo[1,2-a]pyrazin-1-one + 2 AMP + 2 diphosphate + H(+) + H2O + NADP(+) NRP synthetases are composed of discrete domains (adenylation (A), thiolation (T) or peptidyl carrier protein (PCP) and condensation (C) domains) which when grouped together are referred to as a single module. Each module is responsible for the recognition (via the A domain) and incorporation of a single amino acid into the growing peptide product. Thus, an NRP synthetase is generally composed of one or more modules and can terminate in a thioesterase domain (TE) that releases the newly synthesized peptide from the enzyme. Occasionally, methyltransferase domains (responsible for amino acid methylation) are present within the NRP synthetase (By similarity). MalG has the following bimodular architecture: A1-T1-C1-A2-T2-R. MalG finishes with a reductase-like domain (R) for peptide release, which is consistent with the monooxopiperazine moiety of malbrancheamide (PubMed:31548667). Malbrancheamides have the ability to inhibit calmodulin, calmodulin-dependent phosphodiesterase (PDE1), and induce both endothelium-independent and endothelium-dependent relaxant effects, suggesting their potential as vasorelaxant agents. Belongs to the NRP synthetase family.