Isozymes of amino acid naphthylamidase in human haematopoietic cell lines.

The occurrence of isozymes of the proteolytic enzyme amino acid naphthylamidase was investigated in a panel of 44 neoplastic and non-neoplastic haematopoietic cell lines by polyacrylamide gel electrophoresis. Two isozymes (A and C) were common for all lines, whereas different forms of a third isozyme with intermediate electrophoretic mobility (B) appeared in nine lines. Isozyme A seemed to be associated with cell proliferation and was not a marker for malignancy. The appearance of different B isozymes not present in normal peripheral blood lymphocytes, occurred in some Burkitt lymphoma lines and in two non-malignant lines maintained for a long time in culture. In three lines derived from myeloid leukaemia a variant of isozyme B seemed to be a marker for cell origin.