The research group of Tang utilitarian, Shanghai Institute of organic science, Chinese Academy of Sciences has made progress in the study of the catalytic formation of cyclopropyl structural units in natural products by double enzyme system

Although cyclopropylation of non activated carbon carbon double bonds can be achieved by many methods in chemical synthesis, there are few reports on this process in the biosynthesis of natural products Recently, Tang utilitarian, a research group of State Key Laboratory of life organic chemistry, Shanghai Institute of organic chemistry, Chinese Academy of Sciences, reported that a double enzyme system consisting of a hemn family protein (c10p) and a methyltransferase (c10q) jointly catalysed the formation of cyclopropyl structure in CC-1065 during the study of natural product CC-1065 biosynthesis The results were recently published in NAT Commun (DOI: 10.1038/s41467-018-05217-1) CC-1065 family compounds are a kind of natural products with high activity derived from microorganisms and containing cyclopropyl pharmacophores At present, they include CC-1065, glutamine (YTM) and doxycycline They are all natural products of spirocyclopenylcyclohexanedione Through the irreversible alkylation of DNA, the genetic material in the cell can kill the cell (IC 50 is at the level of PM) Therefore, this kind of compounds have attracted extensive attention in the research of antibody coupling targeted therapy In the previous study, Tang utilitarian team reported the biosynthetic gene cluster of CC-1065 (ACS chem Biol., 2017, 12, 1603), and found that a subfamily of gyri like family protein has the property of hydrolyzing CC-1065 and YTM cyclopropyl, which can endow microorganisms with resistance to CC-1065 and YTM (NAT Commun., 2017, 8, 1485) On this basis, the team initially revealed the enzymatic mechanism of cyclopropyl formation in CC-1065 family compounds Firstly, c10p and c10q were found to be necessary for the biosynthesis of CC-1065 cyclopropyl by gene knockout, and the mutants of both genes could accumulate the same cyclopropyl deletion intermediate Then, with the intermediate as the substrate, the double enzyme system composed of reconstructed c10p and c10q can realize the cyclopropylation of the intermediate under strict oxygen free conditions, thus generating CC-1065 In order to explore the catalytic mechanism of cyclopropylation, the team also carried out mass spectrometry detection of key intermediates, CD 3-sam (adenosylmethionine) and D 2O isotope labeling experiments, and point mutation research of key amino acid residues Among them, the detection of the covalent intermediate of Sam substrate led the author to speculate on the existence of S-adenosylmethionine methylene radical, a novel species, and to propose that the double enzyme system jointly catalyzes the formation of CC-1065 cyclopropyl This new mechanism of cyclopropylation not only broadens the understanding of the catalytic reactions of hemn family proteins and methyltransferases, but also implies that S-adenosylmethionine can produce different free radical chemistry The above research results are mainly completed by Jin Wenbing, Ph.D Wu Sheng, Ph.D and Yuan Hua, associate researcher of Tang utilitarian research group This work has been greatly supported by NSFC, Shanghai Science and Technology Commission and the strategic leading science and technology program (class B) of Chinese Academy of Sciences.