Leibniz-Institute for Food Systems Biology at the Technical University of Munich, Lise-Meitner-Str. 34, 85354 Freising, Germany.
Gerd Kobal FRH Consulting LLC, 3124 Rock Cress Lane, Sandy Hook, VA23153, USA.
Food Chem. 2023 Nov 15;426:136492. doi: 10.1016/j.foodchem.2023.136492. Epub 2023 Jun 1.
4-Methylphenol is a food-related odor-active volatile with a high recognition factor, due to its horse stable-like, fecal odor quality. Its ambivalent hedonic impact as key aroma compound, malodor, and semiochemical has spurred the search for its cognate, chemosensory odorant receptors across species. A human odorant receptor for the highly characteristic 4-methylphenol has been elusive. Here, we identified and characterized human receptor OR9Q2 to be tuned to purified 4-methylphenol, but not to its contaminant isomer 3-methylphenol. This highly selective function of OR9Q2 complements an exclusive phenol detection gap in the ancient, most broadly tuned human odorant receptor OR2W1. Moreover, a 4-methylphenol function is evolutionary conserved in phylogenetically related OR9Q2 orthologs from chimpanzee, mouse, and cow. Notably, the cow receptor outperformed human OR9Q2 10-fold in signal strength, consonant with previous reports of 4-methylphenol as a bovine pheromone. Our results suggest OR9Q2 as best sensor for the key food odorant, malodor, and semiochemical 4-methylphenol.
4-甲基苯酚是一种与食物有关的气味活性挥发性物质，具有很高的识别因子，因为它具有马厩般的粪便气味质量。它作为关键香气化合物、恶臭物质和半化学物质的矛盾愉悦影响，促使人们在不同物种中寻找其同源的化学感觉气味受体。一种高度特征性的 4-甲基苯酚的人类气味受体一直难以捉摸。在这里，我们鉴定并表征了人类受体 OR9Q2，它可以被纯化的 4-甲基苯酚调谐，但不能被其污染物 3-甲基苯酚调谐。OR9Q2 的这种高度选择性功能补充了古老的、最广泛调谐的人类气味受体 OR2W1 中独特的酚类检测缺口。此外，来自黑猩猩、老鼠和牛的进化相关 OR9Q2 直系同源物中的 4-甲基苯酚功能在进化上是保守的。值得注意的是，牛的受体在信号强度上比人类 OR9Q2 高出 10 倍，这与先前关于 4-甲基苯酚作为牛信息素的报道一致。我们的结果表明，OR9Q2 是关键食物气味、恶臭物质和半化学物质 4-甲基苯酚的最佳传感器。
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