The carbamate, [3-(3-carbamoylphenyl) phenyl] N-cyclohexyl carbamate(URB597) is a known irreversible inhibitor of fatty acid amide hydrolase (FAAH) which is capable of increasing intracellular endocannabinoid levels to measurable antidepressant and analgesic effects in animal models. Several endocannabinoid-like compounds such as the primary fatty acid amides

(PFAMs) are also important signaling molecules which control many physiological processes and exhibit the characteristic cannabimimetics though the physiological functions of some remain elusive. Thus, PEFAMs remain candidates for examination. Since the initial discovery of URB597, little has been reported on its ability to inhibit the FAAH-dependent metabolism of important PFAM substrates. Also, the mode of inhibition of FAAH hydrolysis of substrates by URB597 has not been characterized. FAAH-2 was expressed in HEK293T cells whereas FAAH was assayed from

rat liver preparations. Activity assay employed was a modification of a high throughput fluorimetric screening method’. URB597 exhibited concentration-dependent inhibition of both FAAH and

FAAH-2 hydrolysis of the 3 PFAMs. The potency (pICso) of URB597 obtained against FAAH activity were 6.6 + 0.1, 6.0 + 0.1 and 6.0 + 0.1 for ODA, ArDA and SyDA. URB597 also inhibited FAAH-2 metabolism of PFAMs ina rank order of ODA > ArDA = SyDA (respective pICso values were 6.90 + 0.10, 6.77 + 0.02 and 6.75 + 0.10). The respective Kn and Vinax values for FAAH were 43.0 + 6.0 uM and 14 + 2 nmol.min'.(mg protein)" for ArDA and 60 + 4 uM and 14 + 1 nmol.min'.(mg protein)' for ODA. Our results suggest that URB597 inhibited FAAH hydrolysis of both ArDA and ODA in  an uncompetitive manner.