Characterization and Purification of T Lymphocyte Aminopeptidase B: A Putative Marker of T Cell Activation

Eur J Immunol. 1993 Aug;23(8):1948-55. doi: 10.1002/eji.1830230833.

Abstract

We have previously described that human T lymphocytes express membrane-associated peptidase activities (Mari et al., EMBO J., 1992, 11:3875). 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 degrees C. However, AP-B activity was found mainly in the cytosolic fraction of Jurkat T cells. Cytosolic T cell 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aminopeptidases / analysis
  • Aminopeptidases / immunology
  • Aminopeptidases / isolation & purification*
  • Aminopeptidases / metabolism
  • Biomarkers
  • Blotting, Western
  • Humans
  • Lymphocyte Activation*
  • Precipitin Tests
  • T-Lymphocytes / enzymology*
  • T-Lymphocytes / immunology
  • Up-Regulation

Substances

  • Biomarkers
  • Aminopeptidases
  • aminopeptidase B