Conversion of the dynorphins to Leu-enkephalin in human spinal cord

This study describes three different endopeptidases in human spinal cord with high affinity for the dynorphins. The enzymes, with strict specificity towards paired basic residues, release Leu-enkephalin and its C-terminal extensions - Arg6 and -Arg6 -Arg7 from the substrate peptides. They differ with regard to molecular size, charge properties, and inhibitory profile. Two of the enzymes show optimal activity at neutral pH, whereas the third enzyme has its activity optimum at pH 5.6. They are all suggested to be of importance for the formation of Leu-enkephalin from prodynorphin.