IDENTIFICATION AND CHARACTERIZATION OF 2 DISTINCT KYOTORPHIN-HYDROLYZING ENZYMES IN RAT-BRAIN

We identified and characterized two kyotorphin-hydrolyzing peptidases (KTPases) in a soluble fraction of rat brain. When the soluble fraction was chromatographed with DEAE-Sephacel, the enzyme activity was resolved into two peaks, which were designated as KTPases I and II in their order of elution. KTPases I and II accounted for 95% and 5% of the KTPase activity in the soluble fraction, respectively. KTPases I and II hydrolyzed kyotorphin with K(m) values of 22-mu-M and 110-mu-M, respectively. By gel filtration, M(r) values of KTPases I and II were determined to be 55 000 and 98 000, respectively. Immunological analyses of KTPase II with an anti-enkephalin aminopeptidase antibody indicated that KTPase II was identical to an enkephalin aminopeptidase with M(r) = 98 000. However, KTPase I was a novel peptidase responsible for the major kyotorphin-degrading activity in the soluble fraction of rat brain.