A novel acid proteinase released by hybridoma cells.

An acid proteinase has been detected in culture supernate of the 9.2.27 murine hybridoma. This enzyme extensively degrades albumin and transferrin during short incubations at pH 3 and below. Limited proteolysis of the 9.2.27 IgG2a appears to occur in the culture supernate. Proteolysis in enhanced at low pH in the presence of urea or 1 M acetic acid. The proteinase activity accumulates in continuous perfusion, total cell recycle cultures, beginning during exponential growth of the hybridoma. It is destroyed by boiling and blocked by pepstatin, but not by inhibitors of cysteine or serine proteinases or by EDTA. The low pH optimum may distinguish this enzyme from the known rat and mouse aspartic acid proteinases including cathepsin D and cathepsin E.