Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key Laboratory of Industrial Microbiology, Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Hubei University of Technology, Wuhan, 430068, China.
Microb Biotechnol. 2021 Jul;14(4):1462-1471. doi: 10.1111/1751-7915.13796. Epub 2021 Apr 1.
The enzymatic conversion of l-methionine (l-Met) into volatile organic sulfur-containing compounds (VOSCs) plays an important role in developing the characteristic aroma of foods. However, the mechanism for the direct conversion of l-Met into VOSCs is still unclear in yeast cells used to make food products. Here, we show that the transcription profile of YALI0C22088g from Yarrowia lipolytica correlates positively with l-Met addition. YALI0C22088g catalyses the γ-elimination of l-Met, directly converting l-Met into VOSCs. YALI0C22088g also exhibits strong C-S lysis activities towards l-cystathionine and the other sulfur-containing compounds and forms a distinct cystathionine-γ-lyase subgroup. We identified eight key amino acid residues in YALI0C22088g, and we inferred that the size of the tunnel and the charges carried by the entrance amino acid residue are the determinants for the enzymatic conversion of l-Met into VOSCs. These findings reveal the formation mechanism of VOSCs produced directly from l-Met via the demethiolation pathway in Yarrowia lipolytica, which provides a rationale for engineering the enzymatic conversion of l-Met into VOSCs and thus stimulates the enzymatic production of aroma compounds.
甲硫氨酸（l-Met）经酶促转化为挥发性含硫有机化合物（VOSCs），在食品特色香气的形成中起着重要作用。然而，在用于制作食品的酵母细胞中，l-Met 直接转化为 VOSCs 的机制仍不清楚。在这里，我们表明，解脂耶氏酵母 YALI0C22088g 的转录谱与 l-Met 的添加呈正相关。YALI0C22088g 催化 l-Met 的γ消除反应，直接将 l-Met 转化为 VOSCs。YALI0C22088g 对 l-胱硫醚和其他含硫化合物也表现出强烈的 C-S 裂解活性，并形成一个独特的胱硫醚-γ-裂合酶亚群。我们鉴定了 YALI0C22088g 中的八个关键氨基酸残基，我们推断隧道的大小和入口氨基酸残基所带的电荷是 l-Met 酶促转化为 VOSCs 的决定因素。这些发现揭示了直接从 l-Met 通过解硫醇途径在解脂耶氏酵母中产生 VOSCs 的形成机制，为工程化 l-Met 酶促转化为 VOSCs 提供了依据，并由此刺激了香气化合物的酶促生产。
