Effect of stimulation on soluble proteolytic enzymes released by peripheral blood mononuclear cells

The release of soluble peptidases active in the degradation of leucine enkephalin by human peripheral blood mononuclear cells (PBMC), and the effect of stimulation of mononuclear cells on the release of these enzymes are reported. Results obtained indicate that leu-enkephalin is partially degraded in the presence of soluble supernatants prepared from mononuclear cells. In accord with data previously obtained with immunocompetent cell lines, three classes of enzymes appear to be involved in leu-enkephalin hydrolysis: aminopeptidases, dipeptidylaminopeptidases and dipeptidylcarboxypeptidases. Phytohemagglutinin stimulation of mononuclear cells appears to cause a relevant increase of the total activity of the soluble enzymes, as well as a partial rearrangement of the ratio between the different enzyme activities. A similar effect is also evident upon chromatographic separation of the soluble supernatants: the relative activity of the several distinct enzymes--notably aminopeptidases and dipeptidylaminopeptidases--identified after column separation is significantly modified by PBMC stimulation. The effect of stimulation of mononuclear cells on the release of soluble enzymes can be interpreted as an indication of the role of these enzymes--possibly in the regulative process of informational peptides--similar to that described in the case of membrane enzymes.