Boll M, Löwel M, Berndt J
Biochim Biophys Acta. 1980 Dec 5;620(3):429-39. doi: 10.1016/0005-2760(80)90134-4.
Lipid-depleted yeast, grown anaerobically, contains only very low amounts of sterols. The hydroxymethylglutaryl-CoA reductase activity, the regulatory enzyme of sterol synthesis in yeast, is also low. Aeration of such cells in a buffer containing a carbon source induces hydroxymethylglutaryl-CoA reductase activity and increases sterol synthesis. The velocity of the increase depends on the carbon source present during the aeration period. Glucose and sugars that are easily converted to glucose were found to be most effective. A supplement of unsaturated fatty acids during anaerobic growth causes a several-fold greater velocity of the enzyme induction and of sterol biosynthesis. Linolenic acid (30 microM) accelerated sterol biosynthesis about 7-fold. Activities of galactokinase and galactose-1-phosphate uridyltransferase, which are involved in the conversion of galactose to glucose, increased several-fold in the supplemented cells within 6 h of aeration, concomitantly with stimulation of sterol synthesis from galactose. It is suggested that the stimulation of enzyme induction and sterol biosynthesis in fatty acid supplemented cells is due to a completion of the protein-synthesizing apparatus during cell growth. A markedly enhanced capacity of these cells to incorporate leucine into acid-precipitable protein supports this assumption.
厌氧培养的脂质缺乏型酵母仅含有极少量的固醇。酵母中固醇合成的调节酶——羟甲基戊二酰辅酶A还原酶的活性也很低。在含有碳源的缓冲液中对这类细胞进行通气会诱导羟甲基戊二酰辅酶A还原酶的活性，并增加固醇的合成。增加的速度取决于通气期间存在的碳源。发现葡萄糖和易于转化为葡萄糖的糖类最为有效。在厌氧生长期间补充不饱和脂肪酸会使酶诱导和固醇生物合成的速度提高几倍。亚麻酸（30微摩尔）使固醇生物合成加速约7倍。参与半乳糖向葡萄糖转化的半乳糖激酶和1-磷酸半乳糖尿苷转移酶的活性，在通气6小时内，在补充细胞中增加了几倍，同时伴随着半乳糖固醇合成的刺激。有人认为，在脂肪酸补充细胞中酶诱导和固醇生物合成的刺激是由于细胞生长期间蛋白质合成装置的完善。这些细胞将亮氨酸掺入酸沉淀蛋白的能力明显增强支持了这一假设。
