Ueda N, Goparaju S K, Katayama K, Kurahashi Y, Suzuki H, Yamamoto S
Department of Biochemistry, University of Tokushima School of Medicine, Japan.
J Med Invest. 1998 Aug;45(1-4):27-36.
Cannabinoids are psychoactive components of marijuana, and bind to specific G protein-coupled receptors in the brain and other mammalian tissues. Anandamide (arachidonoylethanolamide) was discovered as an endogenous agonist for the cannabinoid receptors. Hydrolysis of anandamide to arachidonic acid and ethanolamine results in the loss of its biological activities. The enzyme responsible for this hydrolysis was solubilized, partially purified from the microsomes of porcine brain, and referred to as anandamide amidohydrolase. In addition to the anandamide hydrolysis, the enzyme preparation catalyzed anandamide synthesis by the condensation of arachidonic acid with ethanolamine. Several lines of enzymological evidence suggested that a single enzyme catalyzes both the hydrolysis and synthesis of anandamide. This reversibility was confirmed by the use of a recombinant enzyme of rat liver overexpressed in COS-7 cells. However, in consideration of the high Km value for ethanolamine as a substrate for the anandamide synthesis, the enzyme was presumed to act as a hydrolase rather than a synthase under physiological conditions. The recombinant enzyme acted not only as an amidase hydrolyzing anandamide and other fatty acid amides but also as an esterase hydrolyzing methyl ester of arachidonic acid. 2-Arachidonoylglycerol, which was found recently to be another endogenous ligand, was also efficiently hydrolyzed by the esterase activity of the same enzyme. The anandamide hydrolase and synthase activities were detected in a variety of rat organs, and liver showed by far the highest activities. A high anandamide hydrolase activity was also detected in small intestine but only after the homogenate was precipitated with acetone to remove endogenous lipids inhibiting the enzyme activity. The distribution of mRNA of the enzyme was in agreement with that of the enzyme activity.
大麻素是大麻中的精神活性成分，可与大脑及其他哺乳动物组织中的特定G蛋白偶联受体结合。花生四烯酸乙醇胺（N-花生四烯酸乙醇胺）被发现是大麻素受体的内源性激动剂。花生四烯酸乙醇胺水解为花生四烯酸和乙醇胺会导致其生物活性丧失。负责这种水解的酶被溶解，从猪脑微粒体中部分纯化出来，并被称为花生四烯酸乙醇胺酰胺水解酶。除了花生四烯酸乙醇胺水解外，该酶制剂还通过花生四烯酸与乙醇胺的缩合催化花生四烯酸乙醇胺的合成。几条酶学证据表明，单一酶催化花生四烯酸乙醇胺的水解和合成。通过使用在COS-7细胞中过表达的大鼠肝脏重组酶证实了这种可逆性。然而，考虑到乙醇胺作为花生四烯酸乙醇胺合成底物的高Km值，推测该酶在生理条件下作为水解酶而非合成酶起作用。该重组酶不仅作为水解花生四烯酸乙醇胺和其他脂肪酸酰胺的酰胺酶，还作为水解花生四烯酸甲酯的酯酶起作用。最近发现的另一种内源性配体2-花生四烯酸甘油也被同一酶的酯酶活性有效水解。在多种大鼠器官中检测到花生四烯酸乙醇胺水解酶和合成酶活性，其中肝脏的活性最高。在小肠中也检测到高花生四烯酸乙醇胺水解酶活性，但仅在匀浆用丙酮沉淀以去除抑制酶活性的内源性脂质后。该酶的mRNA分布与酶活性分布一致。
