title: Enkephalin generating activity of rat brain endopeptidases.
abstract: An amphiphilic substrate was used as the basis of a specific assay for peptidases which generate the opioid peptide methionine enkephalin. The substrate [Homoarg-14C]Tyr-Gly-Gly-Phe-Met-Thr-Ser-Glu-Homoarg is prepared by guanidination of the lysine analogue (which is beta-lipotropin 61-69) with O-methyl-[14C]isourea and is quantitatively adsorbed to dextrancoated charcoal. The COOH-terminal tetrapeptide is not adsorbed and, since it carries the radioactive label, is easily assayed in the charcoal-free supernatant fluid. Two enzyme activities have been identified in rat brain which specifically convert the amphiphilic substrate to enkephalin and the resulting tetrapeptide tail. These activities are soluble and particulate, respectively, and differ in regional distribution within the brain, in their inhibition by other peptides and in Km. Based upon these characteristics, it seems likely that the soluble activity is not primarily involved in the biosynthesis of enkephalin. It does seem possible, however, that the particulate activity which we describe may play a role in opioid peptide synthesis from larger precursors.
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D002462:Cell Membrane / Q000201:enzymology; D010450:Endopeptidases / Q000378:metabolism*; D004723:Endorphins / Q000096:biosynthesis*; D004745:Enkephalins / Q000096:biosynthesis*; D007700:Kinetics; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D014018:Tissue Distribution
chemical_list: D004723:Endorphins; D004745:Enkephalins; D010455:Peptides; D010450:Endopeptidases