|Budget Amount *help
¥3,100,000 (Direct Cost : ¥3,100,000)
Fiscal Year 1998 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1997 : ¥2,500,000 (Direct Cost : ¥2,500,000)
Cannabinoids are psychoactive components contained in Cannabis sativa L.and their specific receptors are expressed in brain and other organs. Anandamide (arachidonoylethanolamide) was found as an endogenous ligand for the cannabinoid receptors, and reported to lose its cannabimimetic biological activities by the hydrolysis to arachidonic acid and ethanolamine. In order to elucidate the catalytic properties of anandamide amidohydrolase catalyzing this reaction, COS-7 cells were transfected with cDNA for the rat liver enzyme, and the recombinant enzyme was expressed. The enzyme showed not only the anandamide hydrolase activity but also its reverse reaction, namely, the anandamide synthase activity by the condensation of arachidonic acid with ethanolamine. Both the reactions did not occur in the control COS-7 cells. These results demonstrated the reversibility of the anandamide hydrolysis. However, due to a high Km for ethanolamine, the enzyme seemed to act as an anandamide hydrolase rather than an anandamide synthase under the physiological conditions. In addition to the amidase activity, the enzyme showed an esterase activity for methyl arachidonate.
Therefore, I examined whether or not the enzyme hydrolyzes the ester bond of 2-arachidonoylglycerol (2-AG), another ligand for the cannabinoid receptors. The results showed that the hydrolysis of 2-AG proceeded about 4-fold faster than the anandamide hydrolysis with a Km value as low as 6muM and an optimal pH of IO.This hydrolytic reaction was hardly detected with the control cells. Two compounds inhibited the hydrolysis of both anandamide and 2-AG in parallel, and anandamide inhibited the hydrolysis of 2-AG dose-dependently. These results indicate that anandamide and 2-AG can be degraded by the same enzyme.