Alpha- and beta- rat urinary kallikreins: chemical and physicochemical properties

Alpha- and beta- urinary kallikreins were isolated by affinity chromatography on Sepharose-L-Arg-OMe (E. Silva, C.R. Diniz and M. Mares-Guia, Biochemistry, 13: 4304-4310, 1974). Both enzymes lowered rat arterial blood pressure and contracted the rat uterus. Alpha- and beta-kallikreins consist of single polypeptide chains of 27900 and 24900 daltons and have sedimentation coefficients of 2.49 S and 2.55 S, respectively. The alpha enzyme has 18 amino acid residues more than the beta enzyme and their carbohydrate content is 11.9% and 7.75%, respectively. Neuraminidase treatment removed all sialic acid residues from both forms and this improved their stability in aqueous solution at pH 7.0, 37 degrees C. After electrophoresis on 12% polyacrylamide gels at pH 8.3, followed by activity measurements of gel slices with H-D-Val-Leu-Arg-pNA, two active bands each were detected for alpha and beta-kallikrein, but in different proportions and with different specific activity. On the basis of the rat uterus assay, alpha-kallikrein was three times more active than beta-kallikrein. The amino acid composition of alpha-kallikrein is strikingly similar to that of pig kallikrein B and human urinary kallikrein.