PURIFICATION AND PROPERTIES OF A PROTEASE FROM PENICILLIUM CYANEO-FULVUM

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Abstract
A proteolytic enzyme present in culture filtrates of Penicillium cyaneo-fulvum was purified approximately 100-fold. In the ultracentrifuge the enzyme behaved as a homogeneous protein, but on electrophoresis some contamination was apparent. The molecular weight of the enzyme was estimated to be about 45,000.The protease hydrolyzed casein and denatured haemoglobin, gelatin, and native bovine plasma albumin but not native or denatured ovalbumin. It also coagulated milk. The optimum pH for caseolysis was 9.5 to 11.0. Metal chelating- and sulphydryl-reagents did not affect enzyme activity but zinc and mercurous ions inhibited the enzyme, the inhibition being reversed with ethylenediaminetetraacetic acid (EDTA). Soybean trypsin inhibitor was without effect on the enzyme whereas ovomucoid inhibited the enzyme. Although it is similar in some respects to other alkaline proteases, the P. cyaneo-fulvum enzyme does not appear to be identical with any one of them.