PURIFICATION AND SOME PROPERTIES OF A PROTEASE FROM ALTERNARIA TENUISSIMA

A proteolytic enzyme from the culture fluid of the fungus Alternaria tenuissima has been purified with a method including precipitation with ammonium sulfate, adsorption on fractionated kieselguhr, precipitation with acetone, and gel filtration. The purified enzyme formed needle-shaped crystals during prolonged ultrafiltration and was homogeneous in the ultracentrifuge and in cellulose-acetate-membrane and zone electrophoresis. Its apparent isoelectric point is above pH 10.5. It has a molecular weight of approximately 23,000 as estimated from ultracentrifugation data and 24,750 as calculated from amino acid analyses on the basis of 6 phenylalanine residues. A provisional estimate of the amino acid content shows 253 residues: Trp4, Lys, His, Arg10, Asp18, Thr33, Ser35, Glu12, Pro4, Gly55, Ala22, Half-cys6, Val19, He7, Leu7, Tyr13, and Phe6. No methionine was found. The ultraviolet absorption spectrum showed a maximum at 277 mμ and a minimum at 251 mμ. © 1969.