In plants, lineage-specific metabolites can be created by activities derived from the catalytic promiscuity of ancestral proteins, although examples of recruiting detoxification systems to biosynthetic pathways are scarce. The ubiquitous glyoxalase (GLX) system scavenges the cytotoxic methylglyoxal, in which GLXI isomerizes the α-hydroxy carbonyl in the methylglyoxal–glutathione adduct for subsequent hydrolysis. We show that GLXIs across kingdoms are more promiscuous than recognized previously and can act as aromatases without cofactors. In cotton, a specialized GLXI variant, SPG, has lost its GSH-binding sites and organelle-targeting signal, and evolved to aromatize cyclic sesquiterpenes bearing α-hydroxyketones to synthesize defense compounds in the cytosol. Notably, SPG is able to transform acetylated deoxynivalenol, the prevalent mycotoxin contaminating cereals and foods. We propose that detoxification enzymes are a valuable source of new catalytic functions and SPG, a standalone enzyme catalyzing complex reactions, has potential for toxin degradation, crop engineering and design of novel aromatics.

在植物中，谱系特异性代谢物可以通过源自祖先蛋白质的催化混杂的活动产生，尽管将解毒系统招募到生物合成途径的例子很少。普遍存在的乙二醛酶 (GLX) 系统清除具有细胞毒性的甲基乙二醛，其中 GLXI 将甲基乙二醛-谷胱甘肽加合物中的 α-羟基羰基异构化以进行后续水解。我们表明，跨界的 GLXI 比以前认识的更混杂，并且可以在没有辅助因子的情况下充当芳香酶。在棉花中，一种特殊的 GLXI 变体 SPG 失去了其 GSH 结合位点和细胞器靶向信号，并进化为芳香化带有 α-羟基酮的环状倍半萜，以在细胞质中合成防御化合物。值得注意的是，SPG 能够转化乙酰化脱氧雪腐镰刀菌烯醇，流行的霉菌毒素污染谷物和食品。我们认为解毒酶是新催化功能的重要来源，而 SPG 是一种催化复杂反应的独立酶，具有降解毒素、作物工程和设计新型芳烃的潜力。