since hughes et al . isolated and identified two endogenous pentapeptides , met- and leu-enkephalin , from the brain and found that they acted as agonists at opiate receptors , alpha- , beta- and gamma-endorphins , larger peptides than enkephalins and having morphine-like activity , have been identified in either the brain or pituitary of various species .
C0014294
leu-enkephalin
C0014298
enkephalins