Jiranek V, Langridge P, Henschke P A
Australian Wine Research Institute, Glen Osmond, South Australia.
J Appl Bacteriol. 1996 Sep;81(3):329-36. doi: 10.1111/j.1365-2672.1996.tb04335.x.
The liberation of H2S is a common problem afflicting wine fermentation. Sulphite reductase activity of a commercial wine yeast was investigated to define its involvement in this process. The activity studied here differed from those characterized previously from cider and bakers' yeasts by displaying a greater sensitivity to cold, low ionic strength and possibly, proteolytic action. These differences necessitated the development of a new method of quantification. Through this method, the onset of H2S liberation was shown not to be a result of variations in the levels of sulphite reductase activity. Thus, high levels of activity which occurred during the exponential phase of growth were not necessarily accompanied by the liberation of H2S. Similarly, nitrogen-starved cultures which liberated H2S showed no corresponding increase in sulphite reductase activity from prestarvation levels. In fact, rates of H2S liberation from cultures and in enzyme assays agreed closely. A short-term independence of sulphite reductase activity from culture nitrogen status was therefore evident. The only influence of nitrogen was achieved in its absence when enzyme activity decayed with a half-life (4.25 h) which was comparable to that induced by the presence of cycloheximide (5.75 h). A proposed transcriptional control mechanism mediated by methionine derivatives was only partly effective in this strain although an in vitro inhibitory effect of methionine was implicated. These data therefore support the notion that H2S liberation in response to nitrogen starvation stems from a failure of metabolism to sequester H2S which continues to be formed, at least initially, at prestarvation rates.
硫化氢的释放是困扰葡萄酒发酵的一个常见问题。对一种商业葡萄酒酵母的亚硫酸盐还原酶活性进行了研究，以确定其在这一过程中的作用。此处所研究的活性与先前从苹果酒酵母和面包酵母中鉴定出的活性不同，它对低温、低离子强度以及可能的蛋白水解作用表现出更高的敏感性。这些差异使得开发一种新的定量方法成为必要。通过这种方法，结果表明硫化氢释放的开始并非亚硫酸盐还原酶活性水平变化的结果。因此，在生长指数期出现的高活性水平不一定伴随着硫化氢的释放。同样，释放硫化氢的氮饥饿培养物的亚硫酸盐还原酶活性相对于饥饿前水平并没有相应增加。事实上，培养物中硫化氢的释放速率与酶测定中的速率非常吻合。因此，亚硫酸盐还原酶活性与培养物氮状态在短期内具有独立性这一点很明显。氮的唯一影响是在其不存在时显现出来的，此时酶活性以半衰期（4.25小时）衰减，这与环己酰亚胺存在时诱导的半衰期（5.75小时）相当。尽管蛋氨酸具有体外抑制作用，但一种由蛋氨酸衍生物介导的转录控制机制在该菌株中仅部分有效。因此，这些数据支持了这样一种观点，即响应氮饥饿而释放硫化氢是由于代谢未能隔离继续形成的硫化氢所致，至少在最初阶段，硫化氢仍以饥饿前的速率形成。
