Boyer J, Somma C, Vérine A, L'Hôte C, Finidori J, Merger C, Arnaud J
J Clin Endocrinol Metab. 1981 Jul;53(1):143-8. doi: 10.1210/jcem-53-1-143.
A monoester lipase (MEL) activity (EC 3.1.1.3) is described in human red blood cells (RBC). The lipase acts as a cell-bound enzyme and is able to exert its catalytic activity in vitro toward an exogenously added emulsified substrate. The enzyme activity, which appears to be confined to the cell membrane, is inhibited by Triton X-100. The MEL activity of human RBC is assayed using intact RBC as the enzyme source, with an emulsion of ethyl [3H]oleate (2 mM) as the substrate. The optimum pH for the reaction is 7.8 at 37 C. Lipolytic rates are monitored by quantitation of the amount of [3H]oleic acid released during 20 min of incubation after extraction by means of a liquid-liquid partition system. Suspensions of purified RBC obtained from 161 healthy adult subjects had a MEL activity of 1022 +/- 134 microunits/10(12) RBC (mean +/- SD), with a normal range (+/- 2 SD) between 754-1290 microunits. The individual activity values varied from 733-1490 microunits. The median of the 161 subjects was 1010 microunits/10(12) RB. There was no significant difference between the mean activities of RBC samples from men and women. MEL activity in RBC from the cord blood of 16 normal infants was found to be 43% higher than that in adults, with an average activity of 1458 +/- 174 microunits (mean +/- SD).
人类红细胞（RBC）中存在一种单酯脂肪酶（MEL）活性（EC 3.1.1.3）。该脂肪酶作为一种细胞结合酶，能够在体外对外源添加的乳化底物发挥催化活性。这种酶活性似乎局限于细胞膜，会被 Triton X - 100 抑制。使用完整的红细胞作为酶源，以[3H]油酸乙酯（2 mM）乳液作为底物来测定人类红细胞的 MEL 活性。反应的最适 pH 在 37℃时为 7.8。通过液 - 液分配系统提取后，在孵育 20 分钟期间定量释放的[3H]油酸量来监测脂解速率。从 161 名健康成年受试者获得的纯化红细胞悬液的 MEL 活性为 1022±134 微单位/10(12)个红细胞（平均值±标准差），正常范围（±2 标准差）在 754 - 1290 微单位之间。个体活性值在 733 - 1490 微单位之间变化。161 名受试者的中位数为 1010 微单位/10(12)个红细胞。男性和女性红细胞样本的平均活性之间没有显著差异。发现 16 名正常婴儿脐带血红细胞中的 MEL 活性比成年人高 43%，平均活性为 1458±174 微单位（平均值±标准差）。
