Pyruvate dehydrogenase multienzyme complex PDHc catalyzes
Pyruvate dehydrogenase multienzyme complex (PDHc) catalyzes the oxidative decarboxylation of pyruvate, and subsequently acetylates coenzyme A (CoA) to acetyl-CoA during the tricarboxylic Cilomilast metabolic pathway using thiamine diphosphate (ThDP) and Mg2+ as cofactors. PDHc poses a key role in cyanobacteria cellular metabolism. Pyruvate dehydrogenase complex E1 [PDHc E1, EC188.8.131.52] is the first and most important enzyme during the multienzyme complex composed of three enzymes. The PDHc E1 catalyzes the first step of thiamin diphosphate-dependent oxidative decarboxylation of pyruvate, which is the rate limiting step in the overall reaction catalyzed by the PDHc. It had been reported that PDHc-E1 enzyme was taken as the potent target of antibacterial and antifungal and herbicide for a long time8, 9. These reports showed that cyanobacterial PDHc E1 (Cy-PDHc E1) possibly could be a potential candidate enzymatic target for searching specific algicide to control HCBs. So far, few studies reported about the inhibitors or algicides targeted to the Cy-PDHc E1. It has been reported that cofactor ThDP plays an important role in the oxidative decarboxylation catalyzed by PDHc E1. Currently, based on the structure of ThDP, some of its analogs had been reported as effective inhibitors against plant PDHc E1 or Escherichia coli (E. coli) PDHc E1 in vitro and against herbicide or antifungal or antibacterial activities in vivo (Fig. 1)9, 10, 11, 12, 13. Compound I is an effective inhibitor of Escherichia coli (E. coli) PDHc E1 in vitro in our previous study, but we found that it was almost not effective against Cy-PDHc E1. In order to find the inhibitors of Cy-PDHc E1, structurally diversified inhibitors should be investigated. Based on the structure of the triazole-ThDP analogs and compound I, firstly, considering that benzoic acid and benzoate derivatives have received much attention especially for their structures and biological activities, such as anticancer, antimicrobial activities17, 18, 19, we remained the 2-methylpyrimidine-4-ylamine moiety of triazole ThDP in our new compounds. Then, because the triazole ring moiety has wider biological activities and plays an important role in bio-conjugation due to easily form powerful pharmacophores, we tried to remain the triazole ring from triazole-ThDP analogs in our new compounds. Furthermore, the highly charged pyrophosphate moiety of ThDP analogs leads a bad bioavailability and negligible anti-microbial activity. Our previous studies have been demonstrated that these highly charged pyrophosphate moiety could be replaced with substituted benzene ring to solve the problem and some herbicide and antifungal and antibacterial candidates were found12, 13, 14, 15. So we used benzene ring to substitute the pyrophosphate group and introduced ester group (OCO) as a functional linker to connect the 1, 2, 3-triazole ring with benzene ring. It is very interesting that the optimized compounds showed higher selective inhibition activity against Cy-PDHc E1. These results encouraged us to further design and synthesize a series of ThDP analogs as potential inhibitors of Cy-PDHc E1. In this study, we designed and synthesized a series of (1-((4-amino-2-methyl pyrimidin-5-yl) methyl)-1H-1,2,3-triazol-4-yl) methyl substituted benzoate by remaining the 2- methylpyrimidine-4-ylamine moiety and the triazole ring and using the ester group (OCO) as a functional linker between 1,2,3-triazole ring and substituted benzene ring (Fig. 2). These compounds not only exhibited higher inhibitory activities against Cy-PDHc E1 in vitro, but also had good algicide activities against Synechocystis PCC6803 and Microcystis aeruginosa FACHB905 than that of triazole-ThDP or compound I in viro. Especially compound 8d showed the highest inhibitory activity against Cy-PDHc E1 and the most powerful inhibitory selectivity between Cy-PDHc E1 and porcine PDHc E1. Furthermore, the potential interaction between compound 8d and Cy-PDHc E1 was analyzed by a molecular docking method and site-directed mutagenesis and enzymatic analysis and fluorescence spectral analysis.