Discovery and biosynthesis of karnamicins as angiotensin converting enzyme inhibitors
Zhiyin Yu, Jianping Huang, Jing Yang, Chongxi Liu, Yijun Yan, Li Wang, Junwei Zhao, Yin Chen, Wensheng Xiang, Sheng‐Xiong Huang
Abstract
Abstract Angiotensin-converting enzyme inhibitors are widely used for treatment of hypertension and related diseases. Here, six karnamicins E 1 -E 6 ( 1 – 6 ), which bear fully substituted hydroxypyridine and thiazole moieties are characterized from the rare actinobacterium Lechevalieria rhizosphaerae NEAU-A2. Through a combination of isotopic labeling, genome mining, and enzymatic characterization studies, the programmed assembly of the fully substituted hydroxypyridine moiety in karnamicin is proposed to be due to sequential operation of a hybrid polyketide synthase-nonribosomal peptide synthetase, two regioselective pyridine ring flavoprotein hydroxylases, and a methyltransferase. Based on AlphaFold protein structures predictions, molecular docking, and site-directed mutagenesis, we find that two pyridine hydroxylases deploy active site residues distinct from other flavoprotein monooxygenases to direct the chemo- and regioselective hydroxylation of the pyridine nucleus. Pleasingly, karnamicins show significant angiotensin-converting enzyme inhibitory activity with IC 50 values ranging from 0.24 to 5.81 μM, suggesting their potential use for the treatment of hypertension and related diseases.