Parthasarathy S, Lin J T, Baumann W J
Biochim Biophys Acta. 1979 Apr 27;573(1):107-13. doi: 10.1016/0005-2760(79)90177-2.
The hydrolysis of long-chain monoester of ethanediol by rat,liver subcellular fractions was investigated in order to define the carboxylic acid ester hydrolase involved and to localize the enzymic activity. We found that with 1-O-hexadecanoyl [U-14C]ethanediol as substrate, hydrolytic activity was foremost associated with the rough microsomal fraction. The pH optimum occurred at 8.5. The apparent Km and V values were 6.5 . 10(-4) M and 13 mumol/h per mg microsomal protein, respectively. Enzymic activity was inhibited by p-chloromercuribenzoate and by diisopropylfluorophosphate, whereas NaF was less effective and CaCl2 did not affect apparent activity. Amongst a number of carboxylic acid esters tested as substrate, only long-chain 1-acyl and 2-acyl glycerols inhibited acyl diol hydrolysis competitively (Ki approximately 0.9 mM). It was concluded that long-chain monoesters of ethanediol are hydrolyzed by the monoacyl glycerol lipase system associated with the rat liver microsomal fraction. Because diol monoester is also utilized by the cholinephosphotransferase system of liver to form highly lytic acyl diol phosphocholines, efficient diol monoester hydrolysis by monoglyceride lipase may be a significant step in regulating acyl diol phosphocholine levels in biological systems.
为了确定所涉及的羧酸酯水解酶并定位酶活性，对大鼠肝脏亚细胞组分催化乙二醇长链单酯的水解进行了研究。我们发现，以1-O-十六烷酰基[U-14C]乙二醇为底物时，水解活性主要与粗微粒体组分相关。最适pH为8.5。表观Km和V值分别为6.5×10(-4)M和每毫克微粒体蛋白13μmol/h。对氯汞苯甲酸和二异丙基氟磷酸可抑制酶活性，而氟化钠的抑制作用较弱，氯化钙对表观活性无影响。在作为底物测试的多种羧酸酯中，只有长链1-酰基甘油和2-酰基甘油竞争性抑制酰二醇水解（Ki约为0.9mM）。得出的结论是，乙二醇长链单酯由与大鼠肝脏微粒体组分相关的单酰甘油脂肪酶系统水解。由于二醇单酯也被肝脏的胆碱磷酸转移酶系统利用以形成高溶解性的酰二醇磷酸胆碱，单甘油酯脂肪酶对二醇单酯的高效水解可能是调节生物系统中酰二醇磷酸胆碱水平的重要步骤。
