Characterization and purification of T lymphocyte aminopeptidase B : A putative marker of T cell activation

✍ Scribed by Nathalie Belhacene; Bernard Mari; Bernard Rossi; Patrick Auberger

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 965 KB
• Volume: 23
• Category: Article
• ISSN: 0014-2980
• DOI: 10.1002/eji.1830230833

✦ Synopsis

INSERM U 364, Facult6 de lymphocyte of Tcell

Mkdecine, Nice

We have previously described that human T lymphocytes express membraneassociated peptidase activities (Mari et al., EMBO J., 1992,ll: 3875).We show in this report that intact Jurkat T cells readily cleaved H-Arg-paranitroanilide, an aminopeptidase B (AP-B) substrate.The identification of the hydrolyzing activity as AP-B was confirmed by its sensitivity to both arphamenine B and bestatin in the nanomolar range. Significant AP-B activity was released in the supernatant upon incubation of intact T lymphocytes at 37°C. However, AP-B activity was found mainly in the cytosolic fraction of Jurkat Tcells. CytosolicTcell AP-B was purified to homogeneity and exhibited a molecular mass of 72 kDa. Purified AP-B cleaved N-terminal basic amino acid-containing peptides such as thymopentin (H-Arg-Lys-Asp-Val-Tyr-OH) , indicating that it might play a role in the regulation of the concentration of important soluble mediators of T cell activation. A rabbit polyclonal antibody was shown to recognize AP-B as assessed by both immunoprecipitation and Western blot experiments. Finally, we found that AP-B was up-regulated during activation of normal and leukemic T lymphocytes.