Tripeptide probes for tripeptidyl protease I production via gene transfer

Tripeptides derived from 5-chloroanthraquinone hydrazide and anthraquinone hydrazide have been prepared as potential reagents to probe cellular expression of tripeptidyl protease I (TPP-I). Attempted chemical synthesis of Gly-L-Pro-L-Ala-chloroanthraquinone hydrazide, a compound that had been reported to serve as a substrate for this enzyme, was complicated by formation of a pyrazoloquinone. In contrast, formation of pyrazoloquinones was not observed during coupling reactions with anthraquinone hydrazide, and several tripeptide derivatives of this compound were prepared. The most attractive probe for TPP-I activity in tests with mouse kidney tissue sections proved to be Gly-L-Pro-L-Ser anthraquinone hydrazide.