Fig. 5.

a γ-glutamyl cycle for transporting amino acids coupled to the degradation of glutathione. AA is the amino acid being transported inside the cell by the ɣ-glutamyl transpeptidase, ɣ-GTP. b Reactions involved in creatine/creatinine metabolism and urea cycle coupled to catabolism of L-arginine and L-ornithine. The enzymes involved in the different steps are: AII arginase II, GATM L-arginine:glycine amidinotransferase, ODC ornithine decarboxylase, OAT ornithine, DAO diamine oxidase, MAO monoamino oxidase, GAD glutamic acid decarboxylase, pyrroline-5-carboxylate (PC5) dehydrogenase. c Activation of anandamide synthesis by calcium release. The enzyme involved is a specific phospholipase D (NAPE-PLD)