文章基本信息

标题：Steroidal antibiotics are antimetabolites of Acanthamoeba steroidogenesis with phylogenetic implications
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作者：Wenxu Zhou ; Wenxu Zhou ; Emilio Ramos 等
期刊名称：JLR Papers In Press
印刷版ISSN：0022-2275
电子版ISSN：1539-7262
出版年度：2019
卷号：60
期号：5
页码：981-994
DOI：10.1194/jlr.M091587
出版社：American Society for Biochemistry and Molecular Biology
摘要：Pathogenic organisms may be sensitive to inhibitors of sterol biosynthesis, which carry antimetabolite properties, through manipulation of the key enzyme, sterol methyltransferase (SMT). Here, we isolated natural suicide substrates of the ergosterol biosynthesis pathway, cholesta-5,7,22,24-tetraenol (CHT) and ergosta-5,7,22,24(28)-tetraenol (ERGT), and demonstrated their interference in Acanthamoeba castellanii steroidogenesis: CHT and ERGT inhibit trophozoite growth (EC₅₀ of 51 nM) without affecting cultured human cell growth. Washout experiments confirmed that the target for vulnerability was SMT. Chemical, kinetic, and protein-binding studies of inhibitors assayed with 24- Ac SMT [catalyzing C₂₈-sterol via Δ²⁴⁽²⁸⁾-olefin production] and 28- Ac SMT [catalyzing C₂₉-sterol via Δ²⁵⁽²⁷⁾-olefin production] revealed interrupted partitioning and irreversible complex formation from the conjugated double bond system in the side chain of either analog, particularly with 28- Ac SMT. Replacement of active site Tyr62 with Phe or Leu residues involved in cation-π interactions that model product specificity prevented protein inactivation. The alkylating properties and high selective index of 10³ for CHT and ERGT against 28- Ac SMT are indicative of a new class of steroidal antibiotic that, as an antimetabolite, can limit sterol expansion across phylogeny and provide a novel scaffold in the design of amoebicidal drugs. Animal studies of these suicide substrates can further explore the potential of their antibiotic properties.
关键词：anti-amoeba drugs ; suicide substrate ; sterol biosynthesis