Fatty acid amide hydrolase mediated endocannabinoid signaling in an early land plant, Physcomitrella patens

Fatty acid amide hydrolase (FAAH) belongs to a diverse class of enzymes in amidase signature family. In mammals, FAAH is targeted to affect neurological functions because it terminates endocannabinoid signaling by degrading anandamide, a 20C N -acylethanolamine (NAE 20:4). In higher plants, FAAH is known to modulate growth, development and stress tolerance by degrading 12-18C NAEs. Since anandamide was reported to exclusively occur in early land plants, we investigated its metabolic pathway in the moss Physcomitrella patens. Based on the highest identity with ratFAAH, we identified nine orthologs in moss, Pp FAAH1 to Pp FAAH9. Several bioinformatic tools were used to understand the structural basis of how catalytic residues fold for amidohydrolase activity. Based on these in silico analyses of Pp FAAHhomologs and their gene expression in response to saturated (NAE16:0) and unsaturated NAE (NAE 20:4) treatment, Pp FAAH1was selected for biochemical characterization. Heterologously expressed Pp FAAH1 showed highest amidohydrolase activity at 37°C and pH 8.0. Both in vivo and in vitro studies showed that unsaturated NAE substrate is hydrolyzed faster than the saturated NAE (> 10-fold in vivo and50-fold in vitro ). Additionally, transgenic moss lines over expressing FAAH1 showed slower growth and disrupted gametophyte formation when compared to wild type. These data suggest that Pp FAAH1-mediated NAE metabolism is likely involved in developmental transition in moss.