THE CLONED RAT HYDROLYTIC ENZYME RESPONSIBLE FOR THE BREAKDOWN OF ANANDAMIDE ALSO CATALYZES ITS FORMATION VIA THE CONDENSATION OF ARACHIDONIC-ACID AND ETHANOLAMINE

Anandamide amidase is the hydrolytic enzyme responsible for the breakd own of anandamide, an endogenous cannabimimetic, to arachidonate and e thanolamine. Another enzymatic activity called anandamide synthase cat alyzes the reverse reaction, that is the condensation of arachidonate and ethanolamine. Using a recently cloned rat fatty acid amidohydrolas e (FAAH), we tested the hypothesis that the synthase and the amidase a ctivities are catalyzed by the same enzyme. Untransfected and vector t ransfected (pcDNA3) COS-7 cells did not express detectable levels of e ither the amidase or synthase. However, when COS-7 cells were transien tly transfected with a rat FAAH pcDNA3 construct, both amidase and syn thase were concomitantly expressed. These results indicate that the en zymatic formation of anandamide from arachidonic acid and ethanolamine can be mediated by anandamide amidase acting in the reverse direction . The FAAH transfected cells expressed higher levels of enzyme than ei ther rat brain homogenates or neuroblastoma cells in culture. Furtherm ore, the reaction rate for the amidase in FAAH transfected COS-7 cells , neuroblastoma cells and brain homogenate was always greater than the synthase reaction. These studies raise the question if this synthase reaction serves any physiological role, especially in view of the evid ence that anandamide can be formed by a different pathway. (C) 1997 El sevier Science Ireland Ltd.