Comparison of the heparanase enzymes from mouse melanoma cells, mouse macrophages, and human platelets.

The intracellular heparanases from mouse macrophage and melanoma cells are very similar in terms of their size (60-80 kDa), pI (5.3-4.1), pH optimum (< or = 5.5), and interactions with heparin. These proteins are therefore likely to be identical, suggesting that tumour and blood cells utilise the same heparanase enzyme. The human platelet enzyme is similar to the mouse enzymes in terms of pH optimum (< or = 5.5) and pI value (5.3-4.8), but appears to be smaller in size (40-60 kDa). It also seems to differ from the mouse enzymes in aspects of its surface charge, and in its interactions with heparin. There was no indication that proteolysis was of significance for the enzymes, nor that they contained any sialic acid residues.