Met-enkephalin binding to opiate receptors is not functionally coupled to biodegradation.
Using synaptosomal rat brain membranes, the degradation of Met-enkephalin in both free and receptor-bound form was measured, together with the dissociation of Met-enkephalin from the receptors. The results show that the degradation rate of initially receptor-bound Met-enkephalin is significantly smaller than either the rate of dissociation from the receptors or that of the degradation of free Met-enkephalin. These data suggest that intact Met-enkephalin dissociates from the receptors and then it becomes a target for the same membrane-associated peptidases that split free Met-enkephalin. This view is supported by the good fitness of the measured degradation of initially receptor-bound Met-enkephalin to the predicted degradation curve calculated from the dissociation rate of receptor-bound Met-enkephalin and the degradation rate of free Met-enkephalin.
D000818:Animals; D001921:Brain / Q000378:metabolism*; D004744:Enkephalin, Methionine / Q000378:metabolism*; D007700:Kinetics; D010447:Peptide Hydrolases / Q000378:metabolism*; D051381:Rats; D011957:Receptors, Opioid / Q000378:metabolism*; D013570:Synaptic Membranes / Q000378:metabolism*
D011957:Receptors, Opioid; D004744:Enkephalin, Methionine; D010447:Peptide Hydrolases