Isolation and characterization of an enkephalin-hydrolyzing dipeptidyl-aminopeptidase from calf-brain striatum

Cytosolic dipeptidyl-aminopeptidase with a high affinity for Leu-enkephalin (K m = 5–7 μM) was partially purified from the 25,000 g supernatant of calf-brain striatum. The procedure included pH 4.5 denaturation, DEAE-cellulose chromatography and Blue Sepharose CL-6B chromatography and resulted in preparations that are free from other enkephalin-hydrolyzing enzymes. This enzyme, which is called enkephalinase B, has a positively charged group in its active site and presumably also a Zn atom since the loss in activity induced by EDTA treatment can be restored without loss of substrate affinity by low concentrations of ZnSO 4.