Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao 266003, P. R. China.
Department of Medicinal Chemistry, University of Utah, Salt Lake City, Utah 84112, United States.
J Am Chem Soc. 2022 Jun 1;144(21):9363-9371. doi: 10.1021/jacs.2c01416. Epub 2022 May 19.
Nearly every animal species on Earth contains a unique polyketide synthase (PKS) encoded in its genome, yet no animal-clade PKS has been biochemically characterized, and even the chemical products of these ubiquitous enzymes are known in only a few cases. The earliest animal genome-encoded PKS gene to be identified was 1 from sea urchins. Previous genetic knockdown experiments implicated 1 in synthesis of the sea urchin pigment echinochrome. Here, we express and purify , performing biochemical experiments to demonstrate that the sea urchin protein is responsible for the synthesis of 2-acetyl-1,3,6,8-tetrahydroxynaphthalene (ATHN). Since ATHN is a plausible precursor of echinochromes, this result defines a biosynthetic pathway to the ubiquitous echinoderm pigments and rewrites the previous hypothesis for echinochrome biosynthesis. Truncation experiments showed that, unlike other type I iterative PKSs so far characterized, produces the naphthalene core using solely ketoacylsynthase (KS), acyltransferase, and acyl carrier protein domains, delineating a unique class of animal nonreducing aromatic PKSs (aPKSs). A series of amino acids in the KS domain define the family and are likely crucial in cyclization activity. Phylogenetic analyses indicate that SpPks1 and its homologs are widespread in echinoderms and their closest relatives, the acorn worms, reinforcing their fundamental importance to echinoderm biology. While the animal microbiome is known to produce aromatic polyketides, this work provides biochemical evidence that animals themselves also harbor ancient, convergent, dedicated pathways to carbocyclic aromatic polyketides. More fundamentally, biochemical analysis of SpPks1 begins to define the vast and unexplored biosynthetic space of the ubiquitous animal PKS family.
地球上几乎每一种动物物种的基因组中都包含一种独特的聚酮合酶（PKS），但尚未对任何动物谱系的 PKS 进行生化特征分析，甚至这些无处不在的酶的化学产物也仅在少数情况下为人所知。最早被鉴定的动物基因组编码的 PKS 基因来自海胆。先前的遗传敲低实验表明 1 参与了海胆色素echinochrome 的合成。在这里，我们表达和纯化 ，进行生化实验证明，海胆蛋白负责合成 2-乙酰-1,3,6,8-四羟基萘（ATHN）。由于 ATHN 是 echinochromes 的一个合理前体，因此该结果定义了一个普遍存在的棘皮动物色素生物合成途径，并改写了以前的 echinochrome 生物合成假说。截断实验表明，与迄今为止表征的其他类型 I 迭代 PKS 不同， 仅使用酮酰基合酶（KS）、酰基转移酶和酰基载体蛋白结构域产生萘核心，划定了一类独特的动物非还原芳香 PKS（aPKS）。KS 结构域中的一系列氨基酸定义了家族，并且可能在环化活性中至关重要。系统发育分析表明，SpPks1 及其同源物在棘皮动物及其最亲近的亲戚——橡子蠕虫中广泛存在，这强化了它们对棘皮动物生物学的基本重要性。虽然已知动物微生物组会产生芳香族聚酮化合物，但这项工作提供了生化证据表明，动物本身也拥有古老的、趋同的、专门的碳环芳香族聚酮化合物途径。更根本地说，SpPks1 的生化分析开始定义广泛而未被探索的普遍存在的动物 PKS 家族的生物合成空间。
