Discovery and Biosynthesis of Atrovimycin, an Antitubercular and Antifungal Cyclodepsipeptide Featuring Vicinal-dihydroxylated Cinnamic Acyl Chain

Abstract

Atrovimycin (1), a cyclodepsipeptide containing a unique vicinal-hydroxylated cinnamic acyl chain, was isolated and elucidated from Streptomyces atrovirens LQ13. The biosynthetic pathway of 1 was achieved, revealing cytochrome P450 (Avm43) and epoxide hydrolase (Avm29) enzymes constructing the vicinal-dihydroxy substitution, as well as a tailoring P450 (Avm28) enzyme catalyzing β-hydroxylation of the l-Phe moiety. Atrovimycin shows in vitro antifungal activity and antitubercular activity against Mycobacterium tuberculosis H37Rv both in vitro (with MIC of 2.5 μg/mL) and in vivo.

An Unusual Type II Polyketide Synthase System Involved in Cinnamoyl Lipid Biosynthesis

“…(Figures 1 A, S1). Notably, CL containing compounds display a broad range of physiological activities, including but not limited to antiangiogenic, [7] antitumor, [5] antibacterial, [1] antifungal, [8] antituberculosis, [9, 10] and enzyme inhibitor [11, 12] . For example, atratumycin displays potent antituberculosis activity, [10] skyllamycin A is a potent inhibitor of the platelet‐derived growth factor (PDGF) signaling pathway, [6] and serpentemycin A possesses a strong inhibitory activity against glycosyltransferase [11]…”

“…The CL moiety was proposed to be assembled by a repeating cycle of condensation, reduction, dehydration, isomerization and then cyclization, to give the required product (Figure 1 B). Identification of the biosynthetic gene clusters (BGCs) of CLs and CCNPs indicated that the CL moiety is possibly derived from a type II polyketide synthase (PKS) system [1, 5, 6, 9, 10, 13, 14] . However, unlike the type II aromatic, [15] highly reducing (HR), [16] and acyl polyene (APE) [17] PKSs, CL PKSs not only harbor acyl carrier protein (ACP), ketosynthase (KS), ketoreductase (KR), and dehydratase (DH) (absent in some cases [9] ) domains, but also an isomerase (ISO).…”

“…However, unlike the type II aromatic, [15] highly reducing (HR), [16] and acyl polyene (APE) [17] PKSs, CL PKSs not only harbor acyl carrier protein (ACP), ketosynthase (KS), ketoreductase (KR), and dehydratase (DH) (absent in some cases [9] ) domains, but also an isomerase (ISO). The intriguing benzene ring formation was proposed to be accomplished via 6π‐electrocyclic ring closure followed by dehydrogenation, [18] which was deduced to be catalyzed by the putative oxidoreductase Sky4 or the phytoene dehydrogenase‐like Sky28 in skyllamycin biosynthesis, [6] or by the isomerases Atr16 (atratumycin biosynthesis) and Avm15 (atrovimycin biosynthesis) [9, 10] . However, no in vivo and/or in vitro characterization of the KSs and benzene ring formation have been reported so far, which limits the understanding of the CL PKS system.…”

“…Looking into the youssoufene skeleton, the configuration of the first three double bonds are either trans ‐ or cis ‐form, while the fourth double bond is strictly cis ‐form (Figure 5), suggesting that the isomerization of the fourth double bond is required for further elongation. It is worth to mention that although the isomerase has been proposed to be involved in the formation of the benzene ring, [9–10] no evidence has been reported so far. Although no intermediate harboring the benzene ring was observed in vitro due to unknown reasons, the postulated intermediates n =8, C 18 , 7 (C 20 ), and 8 (C 22 ) were successfully observed through the ITCT experiment developed in this study, thus elucidating the timing of benzene ring formation as indicated in Figure 5.…”

Cinnamic Derivatives as Antitubercular Agents: Characterization by Quantitative Structure–Activity Relationship Studies

“…Cinnamic acid derivatives (CAD) have a century-old history as antitubercular agents [8]. However, this family of compounds was never fully explored for their antimicrobial activity against Mtb, and it was not until a decade ago that some studies were conducted to find novel CAD active against tuberculosis [8][9][10][11][12][13][14][15][16]. Noteworthy, trans-cinnamic acid was found to be bacteriostatic at 200 µg/mL against Mycobacterium smegmatis [9] and was reported to show synergism with some first-line antitubercular agents [9,10,12].…”