Mode of deactivation of the enkephalins by rat and human plasma and rat brain homogenates


SEVERAL groups of workers have recently demonstrated the existence of naturally-occurring peptides which show agonist activity at the opiate receptor1–4, and Hughes et al.5 have shown that the opiate activity isolated by them is due to a mixture of two peptides H–Tyr–Gly–Gly–Phe–Met–OH and H–Tyr–Gly–Gly–Phe–Leu–OH termed methionine-enkephalin and leucine-enkephalin respectively.

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