Lewis T A, Rodriguez R J, Parks L W
Department of Microbiology, North Carolina State University, Raleigh 27695.
Biochim Biophys Acta. 1987 Sep 25;921(2):205-12. doi: 10.1016/0005-2760(87)90020-8.
The relationship between the supply of free sterol and the synthesis of steryl esters by an auxotroph of Saccharomyces cerevisiae has been examined in order to understand the role of cellular free sterol content in the regulatory interactions of sterol esterification. Our results show that the yeast cells must maintain an essential, low level of free sterol that is critical for growth. An additional, expandable pool of free sterol is maintained by the cells, provided there is adequate available sterol. As the quantity of sterol in the expandable pool increases, there is a progressively increasing rate of sterol esterification, which is consistent with the results from in vitro assays of acyl-Co A:ergosterol acyltransferase. Some increases in acyltransferase activity were insensitive to the protein synthetic inhibitor, cycloheximide. The data support the conclusion that sterol interconversion between the free and esterified forms is directed toward maintaining the essential amount of free sterol and that the activity of the relevant sterol enzymes in this organism are modulated in response to intracellular sterol content.
为了了解细胞游离甾醇含量在甾醇酯化调节相互作用中的作用，研究了酿酒酵母营养缺陷型中游离甾醇供应与甾醇酯合成之间的关系。我们的结果表明，酵母细胞必须维持对生长至关重要的、低水平的游离甾醇。如果有足够的可用甾醇，细胞会维持一个额外的、可扩展的游离甾醇池。随着可扩展池中甾醇数量的增加，甾醇酯化速率逐渐增加，这与酰基辅酶A：麦角甾醇酰基转移酶的体外测定结果一致。酰基转移酶活性的一些增加对蛋白质合成抑制剂环己酰亚胺不敏感。数据支持这样的结论，即游离和酯化形式的甾醇相互转化旨在维持游离甾醇的必需量，并且该生物体中相关甾醇酶的活性会根据细胞内甾醇含量进行调节。
