Proline is a predominant amino acid in grape must, but it is poorly utilized by the yeast Saccharomyces cerevisiae in wine‐making processes. This sometimes leads to a nitrogen deficiency during fermentation and proline accumulation in wine. Although the presence of other nitrogen sources under fermentation conditions is likely to interfere with proline utilization, the inhibitory mechanisms of proline utilization remain unclear. In this study, we examined the effect of arginine on proline utilization in S. cerevisiae. We first constructed a proline auxotrophic yeast strain and identified an inhibitory factor by observing the growth of cells when proline was present as a sole nitrogen source. Intriguingly, we found that arginine, and not ammonium ion, clearly inhibited the growth of proline auxotrophic cells. In addition, arginine prevented the proline consumption of wild‐type and proline auxotrophic cells, indicating that arginine is an inhibitory factor of proline utilization in yeast. Next, quantitative polymerase chain reaction (PCR) analysis showed that arginine partially repressed the expression of genes involved in proline degradation and uptake. We then observed that arginine induced the endocytosis of the proline transporters Put4 and Gap1, whereas ammonium induced the endocytosis of only Gap1. Hence, our results may involve an important mechanism for arginine‐mediated inhibition of proline utilization in yeast. The breeding of yeast that utilizes proline efficiently could be promising for the improvement of wine quality.

中文翻译：

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精氨酸对酿酒酵母中脯氨酸利用的抑制作用。

脯氨酸是葡萄汁中的主要氨基酸，但酿酒酵母在酿酒过程中很少利用脯氨酸。这有时会导致发酵过程中氮缺乏和葡萄酒中脯氨酸的积累。尽管在发酵条件下其他氮源的存在可能会干扰脯氨酸的利用，但脯氨酸利用的抑制机制仍不清楚。在这项研究中，我们检查了精氨酸对酿酒酵母中脯氨酸利用的影响. 我们首先构建了脯氨酸营养缺陷型酵母菌株，并通过观察当脯氨酸作为唯一氮源存在时细胞的生长来确定抑制因子。有趣的是，我们发现精氨酸，而不是铵离子，明显抑制了脯氨酸营养缺陷细胞的生长。此外，精氨酸阻止了野生型和脯氨酸营养缺陷型细胞的脯氨酸消耗，表明精氨酸是酵母中脯氨酸利用的抑制因子。接下来，定量聚合酶链反应 (PCR) 分析表明精氨酸部分抑制了参与脯氨酸降解和摄取的基因的表达。然后我们观察到精氨酸诱导脯氨酸转运蛋白 Put4 和 Gap1 的内吞作用，而铵仅诱导 Gap1 的内吞作用。因此，我们的结果可能涉及精氨酸介导的酵母脯氨酸利用抑制的重要机制。有效利用脯氨酸的酵母育种有望提高葡萄酒质量。