CHARACTERIZATION AND CLONING OF TRIPEPTIDYL PEPTIDASE-II FROM THE FRUIT-FLY, DROSOPHILA-MELANOGASTER

We describe the characterization, cloning, and genetic analysis of tri peptidyl peptidase II (TPP II) from Drosophila melanogaster. Mammalian TPP II removes N-terminal tripeptides, has wide distribution, and has been identified as the cholecystokinin-degrading peptidase in rat bra in. Size exclusion and ion exchange chromatography produced a 70-fold purification; of dTPP II activity from Drosophila tissue extracts. The substrate specificity and the inhibitor sensitivity of dTPP II is com parable to that of the human enzyme. In. particular, dTPP II is sensit ive to butabindide, a specific inhibitor of the rat cholecystokinin-in activating activity. We isolated a 4309-base pair dTPP II cDNA which p redicts a 1354-amino acid protein. The deduced human and Drosophila TP P II proteins display 38% overall identity. The catalytic triad, its s pacing, and the sequences that surround it are highly conserved; the C -terminal end of dTPP II contains a 100-amino acid insert not found in the mammalian proteins. Recombinant dTPP II displays the predicted ac tivity following expression in HEK cells. TPP II maps to cytological p osition 49F4-7; animals deficient for this interval show reduced TPP I I activity.