Riley D J, Kyger E M, Spilburg C A, Lange L G
Cardiology Division, Jewish Hospital of St. Louis, Washington University Medical Center, Missouri 63110.
Biochemistry. 1990 Apr 24;29(16):3848-52. doi: 10.1021/bi00468a007.
Human pancreatic fatty acid ethyl ester synthase has been isolated and purified 1200-fold to homogeneity, and its activities, binding properties, and N-terminal amino acid sequence indicate that it is a member of the lipase family. This 52-kDa monomeric protein is present at 0.6-1.2 mg/g of pancreas, and it catalyzes the synthesis and hydrolysis of ethyl oleate at rates of 2400 nmol mg-1 h-1 and 30 nmol mg-1 h-1, respectively. Kinetic analyses reveal a pronounced substrate specificity for unsaturated octadecanoic fatty acids, with ethyl ester synthetic rates of 2400 nmol mg-1 h-1 (linoleic), 2400 nmol mg-1 h-1 (oleic), 400 nmol mg-1 h-1 (arachidonic), 300 nmol mg-1 h-1 (palmitic), and 100 nmol mg-1 h-1 (stearic). Like cholesterol esterase, the enzyme binds to immobilized heparin, and this property was critical for its purification to homogeneity. Its N-terminal amino acid sequence is virtually identical with that reported for human triglyceride lipase, NH2-X-Glu-Val-Cys-5Tyr-Glu-Arg-Leu-Gly-10Cys-Phe-Ser-Asp- Asp-15Ser-Pro-Trp-Ser-Gly-20Ile, and it differs by only four residues from that reported for porcine pancreatic lipase. The synthase purified here also cleaves triglycerides, hydrolyzing triolein at a rate of 30 nmol mg-1 h-1, and this activity is stimulated by colipase and inhibited by sodium chloride. Conversely, commercially available porcine triglyceride lipase exhibits fatty acid ethyl ester synthase activity (1530 nmol mg-1 h-1) and hydrolyzes triolein at a rate of 23 nmol mg-1 h-1.(ABSTRACT TRUNCATED AT 250 WORDS)
人胰腺脂肪酸乙酯合酶已被分离并纯化至1200倍的纯度且达到均一性，其活性、结合特性及N端氨基酸序列表明它是脂肪酶家族的一员。这种52 kDa的单体蛋白在胰腺中的含量为0.6 - 1.2 mg/g，它催化油酸乙酯的合成与水解，速率分别为2400 nmol mg⁻¹ h⁻¹和30 nmol mg⁻¹ h⁻¹。动力学分析显示其对不饱和十八碳脂肪酸具有显著的底物特异性，乙酯合成速率分别为：2400 nmol mg⁻¹ h⁻¹（亚油酸）、2400 nmol mg⁻¹ h⁻¹（油酸）、400 nmol mg⁻¹ h⁻¹（花生四烯酸）、300 nmol mg⁻¹ h⁻¹（棕榈酸）以及100 nmol mg⁻¹ h⁻¹（硬脂酸）。与胆固醇酯酶类似，该酶可结合固定化肝素，此特性对其纯化至均一性至关重要。其N端氨基酸序列与报道的人甘油三酯脂肪酶几乎完全相同，即NH₂ - X - Glu - Val - Cys - 5Tyr - Glu - Arg - Leu - Gly - 10Cys - Phe - Ser - Asp - Asp - 15Ser - Pro - Trp - Ser - Gly - 20Ile，与报道的猪胰腺脂肪酶仅相差四个残基。此处纯化的合酶也能水解甘油三酯，以30 nmol mg⁻¹ h⁻¹的速率水解三油酸甘油酯，该活性受辅脂酶刺激并受氯化钠抑制。相反，市售猪甘油三酯脂肪酶具有脂肪酸乙酯合酶活性（1530 nmol mg⁻¹ h⁻¹），并以23 nmol mg⁻¹ h⁻¹的速率水解三油酸甘油酯。（摘要截选至250字）
