Friedberg S J, Weintraub S T, Singer M R, Greene R C
J Biol Chem. 1983 Jan 10;258(1):136-42.
We have previously presented evidence for the formation of 1-O-alkyl dihydroxyacetone-P from acyl dihydroxyacetone-P via the initial formation of an intermediate 1-O-acyl endiol of acyl dihydroxyacetone-P. This reaction involves a stereospecific exchange of the pro-R hydrogen of the acyl dihydroxyacetone-P moiety without change in configuration. The fatty acid is replaced by a long chain fatty alcohol which retains the oxygen of the primary carbinol. In the absence of fatty alcohol, water substitutes and the product is dihydroxyacetone-P which has also exchanged the pro-R hydrogen with a hydrogen from the medium. An absolute requirement of the proposed mechanism is that the loss of the fatty acid must proceed via an unusual cleavage of the dihydroxyacetone-P C-1 to oxygen bond instead of the usual cleavage at the fatty acid acyl to oxygen bond. In the present investigation, we have synthesized hexadecanoyl dihydroxyacetone-P containing oxygen-18 exclusively at the dihydroxyacetone-P C-1 oxygen. Using this substrate, we have shown that cleavage of hexadecanoyl dihydroxyacetone-P at the C-1 to oxygen bond is linked to O-alkyl dihydroxyacetone-P synthesis. Inhibition of O-alkyl lipid synthesis by means of magnesium or NADPH inhibited the unusual cleavage. At the same time, we have shown that there was hydrolysis of acyl dihydroxyacetone-P which proceeded by the usual mechanism and which was not related to synthesis of O-alkyl dihydroxyacetone-P.
我们之前已经提出证据，证明通过酰基二羟基丙酮 -P 的中间体 1-O-酰基烯二醇的初始形成，可从酰基二羟基丙酮 -P 形成 1-O-烷基二羟基丙酮 -P。该反应涉及酰基二羟基丙酮 -P 部分的前-R 氢的立体定向交换，而构型不变。脂肪酸被长链脂肪醇取代，该脂肪醇保留了伯甲醇的氧。在没有脂肪醇的情况下，水替代，产物是二羟基丙酮 -P，其也已将前-R 氢与介质中的氢进行了交换。所提出机制的一个绝对要求是，脂肪酸的损失必须通过二羟基丙酮 -P 的 C-1 至氧键的异常断裂进行，而不是通过脂肪酸酰基至氧键的通常断裂。在本研究中，我们合成了仅在二羟基丙酮 -P 的 C-1 氧处含有氧 -18 的十六烷酰二羟基丙酮 -P。使用该底物，我们已表明十六烷酰二羟基丙酮 -P 在 C-1 至氧键处的断裂与 O-烷基二羟基丙酮 -P 的合成相关。通过镁或 NADPH 抑制 O-烷基脂质合成可抑制这种异常断裂。同时，我们已表明存在通过通常机制进行的酰基二羟基丙酮 -P 的水解，且其与 O-烷基二羟基丙酮 -P 的合成无关。
