Hybrid PKS-NRPS synthetase; part of the gene cluster that mediates the biosynthesis of the trans-fused decalin-containing tetramic acid phomasetin, the stereochemical opposite of the HIV-1 integrase inhibitor equisetin (PubMed:29972614). The PKS module of phm1 together with the enoylreductase phm4 catalyze the formation of the polyketide unit which is then conjugated to L-serine by the condensation domain of the phm1 NRPS module (PubMed:29972614). Activity of the Dieckmann cyclase domain (RED) of phm1 results in release of the Dieckmann product intermediate (PubMed:29972614). The Diels-Alderase phm7 then uses the Dieckmann product of phm1 as substrate and catalyzes the Diels-Alder cycloaddition to form the decalin ring of N-desmethylphomasetin (PubMed:29972614, PubMed:34121297). N-desmethylphomasetin is further methylated to phomasetin by the methyltransferase phm5 (PubMed:29972614). Secondary metabolite biosynthesis. 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, epimerase (E) domains (responsible for L- to D- amino acid conversion) are present within the NRP synthetase. CcsA contains also a polyketide synthase module (PKS) consisting of several catalytic domains including a ketoacyl synthase domain (KS), an acyl transferase domain (AT), a dehydratase domain (DH), a methyltransferase domain (MT), and a ketoreductase domain (KR). Instead of a thioesterase domain (TE), phm1 finishes with a reductase-like domain (R) for peptide release. Phm1 has the following architecture: KS-MAT-DH-MT-KR-PCP-C-A-T-R. Impairs the production of phomasetin (PubMed:29972614). Phm7 are involved in control of the stereochemistry at C3 and C6 during trans-decalin formation (PubMed:29972614). In the C-terminal section; belongs to the NRP synthetase family.