Proteolytic specificity of elastase on bovine alpha(s1)-casein

Proteases from polymorphonuclear leukocytes (PMN or neutrophils) and macrop hages, the main somatic cells found in milk of healthy cows, may contribute to hydrolysis of caseins at neutral or acid pH in high somatic cell count milks. The objective of this study was to determine the cleavage specificit y of elastase, one of the principal PMN proteinases, on alpha(s1)-casein. a lpha(s1)-Casein (5 mg ml(-1)) was dissolved in phosphate buffer, pH 7.5, an d elastase added. Samples were taken over a 24 h period and analyzed by ure a polyacrylamide gel electrophoresis and high performance liquid chromatogr aphy. Twenty-five cleavage sites were identified showing that elastase had a broad cleavage specificity on alpha(s1)-casein. (C) 2000 Elsevier Science Ltd. All rights reserved.