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Purification of a Protease Secreted by Colletotrichum lindemuthianum. Stephen M. Ries, Postdoctoral Research Associate, Department of Chemistry, University of Colorado, Boulder 80302, Present address of senior author: Department of Plant Pathology, University of Illinois, Urbana 61801; Peter Albersheim, Professor, Department of Chemistry, University of Colorado, Boulder 80302. Phytopathology 63:625-629. Accepted for publication 6 December 1972. DOI: 10.1094/Phyto-63-625.

Colletotrichum lindemuthianum secretes a proteolytic enzyme into culture medium when grown on plant cell walls or on an artificial medium of salts supplemented with collagen as the nitrogen source and glucose as the carbon source. Protease activity has been assayed using a collagen-red dye compound (Azocoll) as substrate. Maximal extracellular protease activity on the glucose-collagen medium occurs after 7 days growth. The protease has been purified from extracellular proteins by (NH₄)₂SO₄ fractionation, ion-exchange chromatography on sulphoethyl Sephadex, and by passage through a polyacrylamide sizing column. The protease has a molecular weight of 25,000 as determined by gel filtration, exhibits optimum activity at pH 8.6, and is stable for several months at 0 C. This is the first reported proteolytic enzyme from a plant pathogen that has been extensively purified and characterized.