Purification and characterization of an alkaline proteinase from kidney cortex lysosomes

An alkaline proteinase was purified to apparent homogeneity from buffalo (Bubalus bubalis) kidney cortex lysosomes by affinity chromatography on STI sepharose 4B and gel filtration over Sephadex G-100. The molecular weight of the enzyme was 17,000 and 21,000 by gel filtration and SDS/PAGE respectively. The purified enzyme was optimally active at pH 8.5-9.0 at 50 degrees C and hydrolysed synthetic substrates of chymotrypsin but not those of elastase or trypsin. It was inhibited by serine proteinase inhibitors like soybean trypsin inhibitor, limabean trypsin inhibitor and phenylmethyl sulphonyl fluoride. Immunologically, the enzyme was similar to chymotrypsin. The amino acid composition showed high content of acidic amino acids. This protein was detected in kidney, liver, spleen, pancreas and heart.