Proteolytic specificity of elastase on bovine β-casein

作     者：Considine, T Healy, A Kelly, AL McSweeney, PLH 

作者机构：Natl Univ Ireland Univ Coll Cork Dept Food Sci & Technol Cork Ireland Natl Univ Ireland Univ Coll Cork Natl Food Biotechnol Ctr Cork Ireland 

出 版 物：《FOOD CHEMISTRY》 (食品化学)

年 卷 期：1999年第66卷第4期

页      面：463-470页

核心收录：

学科分类：0832[工学-食品科学与工程（可授工学、农学学位）] 1004[医学-公共卫生与预防医学(可授医学、理学学位)] 08[工学] 0703[理学-化学] 

基　　金：EU FAIR 

主　　题：elastase beta-casein specificity somatic cells 

摘      要：The lysosomes of the principal somatic cell type recruited on mastitic infection, polymorphonuclear leucocytes (PMN), contain a wide range of hydrolytic enzymes which aid in the destruction of ingested bacteria. These enzymes are of increasing interest in terms of milk quality, but little is known about their activity on the caseins. The objective of this study was to determine the cleavage specificity of elastase, one of the principal PMN proteinases, on beta-casein. beta-casein (5 mg ml(-1)) was dissolved in 0.1 M phosphate buffer, pH 7.5 and 1.76x10(-3) U ml(-1) of elastase were added. Samples were taken over a 24 h period and analysed by urea polyacrylamide gel electrophoresis and high performance liquid chromatography. Peptides were identified by N-terminal sequencing and mass spectrometry. Elastase cleaved p-casein at several sites including Ile(26)-Asn(27), Gln(40)-Thr(41), IIe(49)-His(50), Phe(52)-Ala(53), Gln(56)Ser(57), Leu(58)-Val(59), Asn(68)-Ser(69), Val(82)-Val(83), Val(95)-Ser(96), Ser(96)-Lys(97), Lys(97)-Val(98), Al-101-Met(102), Glu(108)-Met(109), Phe(52)-Thr(120), Glu(131)-Asn(132), Leu(163)-Ser(164), Ala(189)-Phe(190), Phe(190)-Leu(191) and Pro(204)-Phe(205) Some of these sites are also cleaved by chymosin, plasmin or the cell envelope-associated proteinase of Lactococcus. The results show that elastase has a broad specificity on beta-casein and it is therefore possible that indigenous elastase in milk may be of significance to the proteolysis of milk proteins. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.