Purification and characterisation of an 'elastase-like' enzyme from rabbit polymorphonuclear leucocytes

An enzyme with proteolytic activity has been isolated from the subcellular granules of rabbit polymorphonuclear leucocytes. Purification of the enzyme involved extraction of the granule membranes with 0.01 M sodium phosphate buffer, pH 7.4, containing 1 M NaCl and 0.1% Triton X-100, followed by gel exclusion chromatography on Sephadex G-75. The enzyme hydrolysed p-nitrophenol-N-tert-butyloxylcarbonyl-L-alaninate, a synthetic substrate for elastase, but failed to hydrolyse elastin. The enzyme also hydrolysed azo-albumin with a pH optimum between 7.5 and 8.5. Inhibition studies indicated that the enzyme was a serine proteinase (EC 3.4.21.-) and it was found to have an apparent molecular weight of 25 000 by polyacrylamide gel electrophoresis. The purified enzyme behaved as a single on SDS-polyacrylamide gel electrophoresis, had a single isolectric point at pH 5.9, yet showed multiple components on centrifugation.