A novel serine proteinase (HuTSP) isolated from a cloned human CD8+ cytolytic T cell line is expressed and secreted by activated CD4+ and CD8+ lymphocytes

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Abstract
A novel proteinase, termed human T cell-associated serine proteinase (HuTSP), has been highly purified from a human CD8+ T lymphocyte clone. By using a panel of chromogenic model peptide substrates the enzyme was found to specifically recognize L-arginine and to cleave Tos-Gly-Pro-Arg-nitroanilide with high efficiency at a pH optimum of 10.5–11. Exposure to class-specific proteinase inhibitors revealed that HuTSP is a serine endopeptidase. The enzyme has a mol. mass of ∼ 50 kDa (non-reduced) and of ∼ 25–30 kDa (reduced) when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggesting HuTSP to be a disulfide-linked dimer. The enzyme is shown to be inducible by lectin in both CD4+ and CD8+ lymphocytes. Moreover, HuTSP was detected in a number of independent CD4+ and CD8+ T cell clones and was found to be released from effector cells upon ligand binding to the CD3-T cell receptor complex.