Hybrid PKS-NRPS synthetase; part of the gene cluster that mediates the biosynthesis of tenellin-type 2-pyridones, iron-chelating compounds involved in iron stress tolerance, competition with the natural competitor fungus Metarhizium robertsii and insect hosts infection (PubMed:17216664, PubMed:18266306, PubMed:20575135, PubMed:34903054). TenS catalyzes the assembly of the polyketide-amino acid backbone (PubMed:18266306, PubMed:34903054). Because tenS lacks a designated enoylreductase (ER) domain, the required activity is provided the enoyl reductase tenC (PubMed:18266306, PubMed:34903054). Upon formation of the polyketide backbone on the thiotemplate, the triketide is transferred to the NRPS module and linked to tyrosine to produce the pyrrolidine-2-dione intermediates, including pretellinin A, 11-hydropretellenin A, 12-hydropretellenin A, 13-hydropretellenin A, 14-hydropretellenin A, 12-oxopretellenin A and prototellinin D (PubMed:18266306, PubMed:34903054). The pathway begins with the assembly of the polyketide-amino acid backbone by the hybrid PKS-NRPS tenS with the help of the enoyl reductase tenC. These enzymes catalyze the synthesis of the pyrrolidine-2-dione intermediates pretellinin A, 11-hydropretellenin A, 12-hydropretellenin A, 13-hydropretellenin A, 14-hydropretellenin A, 12-oxopretellenin A and prototellinin D. The cytochrome P450 monooxygenase tenA then catalyzes an oxidative ring expansion of pretenellin A and 14-hydropretellenin A to form the 2-pyridone core, leading to pretenellin B and pyridovericin, respectively. The cytochrome P450 monooxygenase tenB is then required for the selective N-hydroxylation of the 2-pyridone nitrogen of yield tellinin and 15-hydroxytellenin (15-HT), respectively. The UDP-glucosyltransferase GT1 and the methyltransferase MT1, located outside the tenS gene cluster, contribute to the stepwise glycosylation and methylation of 15-HT to obtain the glycoside pyridovericin-N-O-(4-O-methyl-beta-D-glucopyranoside) (PMGP). Additional related compounds such as 1-O-methyl-15-HT, (8Z)-1-O-methyl-15-HT, and O-methyltenellin A are also produced but the enzymes involved in their biosynthesis have still to be determined (PubMed:34903054). Secondary metabolite biosynthesis. Expression is positively regulated by the cluster-specific transcription factor tenR and is induced during cocultures with the natural competitor fungus Metarhizium robertsii. 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. TenS contains also a polyketide synthase module (PKS) consisting of several catalytic domains including a ketoacyl synthase domain (KS), a malonyl-CoA:ACP transacylase domain (MAT), a dehydratase domain (DH), a methyltransferase domain (MT), and a ketoreductase domain (KR). Instead of a thioesterase domain (TE), tenS finishes with a reductase-like domain (RED) for peptide release. TenS has the following architecture: KS-MAT-DH-MT-KR-PCP-C-A-T-RED. Impairs the production of tenellin-type 2-pyridones and their intermediates. In the C-terminal section; belongs to the NRP synthetase family.