Fatty Acid Amide Hydrolase 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, PpFAAH1 to PpFAAH9. 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 PpFAAH homologs and their gene expression in response to saturated (NAE16:0) and unsaturated NAE (NAE 20:4) treatment, PpFAAH1 was selected for biochemical characterization. Heterologously expressed PpFAAH1 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 (\u3e 10-fold in vivo and 50-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 PpFAAH1-mediated NAE metabolism is likely involved in developmental transition in moss