Cytochrome P450 monooxygenase; 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:19067514, PubMed:20575135, PubMed:34903054). TenA catalyzes an oxidative ring expansion of pretenellin A and 14-hydropretellenin A to form the 2-pyridone core, leading to the production of pretenellin B and pyridovericin, respectively (PubMed:19067514, 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. Fails to produce tenellin, and leads to the accumulation of 11-hydropretellenin A, 12-hydropretellenin A, 13-hydropretellenin A, 14-hydropretellenin A, 12-oxopretellenin A and prototellinin D. Belongs to the cytochrome P450 family.