Peptidase Activities of Tripeptidyl Peptidase Ⅰ (TPP Ⅰ ) : Exopeptidase and Endopeptidase

摘要

The defect of TPP I causes a disease, late infantile neuronal ceroid lipofuscinosis( LINCL, CLN2). To investigate the bio-activity of tripeptidyl peptidase Ⅰ ( TPP Ⅰ ) from rat kidneys, the effects of digestion of angiotensin Ⅱ (Ang Ⅱ ) and a synthetic endo-type substrate ( Gly~1 -Lys-Pro-Iie-Pro~5 -Phe-Phe-Arg-Leu-Lys~(10) ) via TPP Ⅰ were analyzed by HPLC and TOF-MS. The data suggest that the degradation rate of Ang Ⅱ can reach 18. 2% by the rat TPP Ⅰ and DRV(Asp-Arg-Val) can be released from N-termini of Ang Ⅱ within 16 h. In addition, the synthetic endo-type substrate is cleaved at the same position between Phe~6 and Phe~7. Accordingly, TPP Ⅰ shows two kinds of peptidase activities. One is a tripeptidyl peptidase activity and the other is a pepstatin insensitive carboxyl endopeptidase activity. Tripeptidyl peptidase activity and pepstatin insensitive carboxyl endopeptidase activity seem to be dual phases of one enzyme, TPP Ⅰ .