BIOSYNTHESIS OF ERGOSTEROL IN YEAST - EVIDENCE FOR MULTIPLE PATHWAYS
BIOSYNTHESIS OF ERGOSTEROL IN YEAST - EVIDENCE FOR MULTIPLE PATHWAYS
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DOI：
10.1021/ja00798a051
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发表时间：
1973-01-01
影响因子：
15
通讯作者：
OEHLSCHLAGER, AC
中科院分区：
文献类型：
--
作者：
FRYBERG, M;UNRAU, AM;OEHLSCHLAGER, AC
研究了羊毛甾醇在酿酒酵母中转化为麦角甾醇的反应。对甾醇含量的时程分析和对可疑中间体的捕食实验导致在麦角固醇生物合成的后期阶段发现了几种替代途径。酵母菌在厌氧条件下的维持会耗尽生物体中的甾醇含量。在这些条件下，消耗最快的甾醇是那些具有6.7不饱和度的。在厌氧维持过程中，积累了苦参烯。随之而来的是有氧条件的改变，同时也伴随着固醇的加速产生。对曝气过程中甾醇组成变化的时程分析表明，羊毛甾醇形成后的初始结构改变包括C4和C4的核去甲基化以及C24的烷基化。为了考察后续的修饰，合成了具有不同不饱和度的可疑4，14-脱甲基-24-烷基甾醇中间体(未标记和14C或~3H标记)，如8、7、6-7和24(28)。对酿酒酵母甾醇混合物的层析分离和分析导致在该生物体中发现了五种以前未报道的甾醇(14和16-19)。用预期的中间体和以前报道的酵母甾醇进行的摄食和捕集实验表明，在羊毛甾醇生物转化为麦角甾醇的后期阶段，有几种替代途径是可行的。根据相对掺入效率，从麦角甾醇到麦角甾醇的主要途径是8-7异构化，不饱和引入。
The conversion of lanosterol to ergosterol in Saccharomyces cerevisiae has been investigated. Time-course analysis of the sterol content and feeding-trapping experiments with suspected intermediates led to the discovery of several alternative pathways in the latter stages of ergosterol biosynthesis. Maintenance of the yeast under anaerobic conditions depleted the sterolcontent of the organism. The sterols most rapidly consumed under these conditions were those possessing 6· 7 unsaturation. During anaerobic maintenancesqualene accumu-lated. A subsequent change to aerobic conditions was accompanied by accelerated sterol production. Time-course analysis of the changing sterol compositionduring aeration indicated that the initial structural modifications following the formation of lanosterol involved nuclear demethylation at C4 and Ci4 as well as alkylation atC24. In order to investigate subsequent modifications synthesis of suspected 4, 14-desmethyl-24-alkyl sterol inter-mediates (unlabeled and 14C or3H labeled) possessing varied unsaturation, eg, 8, 7, 6-7, and 24 (28), was carried out. Chromatographic separation and analysis of S. cerevisiae sterol mixtures led to the discovery of five previously unreported sterols (14 and 16-19) in this organism. Feeding and trapping experiments with sus-pected intermediates and previously reported yeast sterols revealed that several alternative pathways are operative in the latter stages of the lanosterol to ergosterol bioconversion. Based on relative incorporation efficiencies, the major route from fecosterol to ergosterol involves 8 7 isomerization, introduction of unsaturation at