TY - JOUR
T1 - Camel and bovine chymosin hydrolysis of bovine aSI- and ß-caseins studied by comparative peptide mapping
AU - Møller, Kirsten Kastberg
AU - Rattray, Fergal Patrick
AU - Ardö, Ylva Margareta
PY - 2012/11/14
Y1 - 2012/11/14
N2 - In many cheese varieties, the general proteolytic activity of the coagulant is of great importance to the development of flavor and texture during ripening. This study used capillary electrophoresis and LC-MS/MS to compare the in vitro proteolytic behavior of camel and bovine chymosin (CC/BC) on bovine αS1- and β-casein (CN) at pH 6.5 and 30 °C. β- CN hydrolysis was also studied at pH 5.2 and in the presence of 0, 2, and 5% (w/v) NaCl. A total of 25 αS1- and 80 β-CN peptides were identified, and initial rates of early peptide formation were determined. The modes of proteolytic action of CC and BC shared a high degree of similarity generally. However, except for a few peptide bonds, CC was markedly less active, the magnitude of which varied widely with cleavage site. Preferential αS1-CN (Phe23?Phe24) and β-CN (Leu192?Tyr193) hydrolysis by CC proceeded at an estimated 36 and 7% of the initial rate of BC, respectively. The latter rate difference was largely pH and NaCl independent. Several cleavage sites appeared to be unique to CC and especially BC action, but qualitative differences were often predetermined by quantitative effects. In particular, negligible CC affinity to αS1-CN164/165 and β-CN189/190 prevented further exposure of the N-terminal products. β-CN hydrolysis by either enzyme was always stimulated at the lower pH, yet either inhibited or stimulated by the presence of NaCl, depending mainly on the predominating type of molecular substrate interactions involved at the specific site of cleavage. The potential impact of this proteolytic behavior on cheese quality is discussed.
AB - In many cheese varieties, the general proteolytic activity of the coagulant is of great importance to the development of flavor and texture during ripening. This study used capillary electrophoresis and LC-MS/MS to compare the in vitro proteolytic behavior of camel and bovine chymosin (CC/BC) on bovine αS1- and β-casein (CN) at pH 6.5 and 30 °C. β- CN hydrolysis was also studied at pH 5.2 and in the presence of 0, 2, and 5% (w/v) NaCl. A total of 25 αS1- and 80 β-CN peptides were identified, and initial rates of early peptide formation were determined. The modes of proteolytic action of CC and BC shared a high degree of similarity generally. However, except for a few peptide bonds, CC was markedly less active, the magnitude of which varied widely with cleavage site. Preferential αS1-CN (Phe23?Phe24) and β-CN (Leu192?Tyr193) hydrolysis by CC proceeded at an estimated 36 and 7% of the initial rate of BC, respectively. The latter rate difference was largely pH and NaCl independent. Several cleavage sites appeared to be unique to CC and especially BC action, but qualitative differences were often predetermined by quantitative effects. In particular, negligible CC affinity to αS1-CN164/165 and β-CN189/190 prevented further exposure of the N-terminal products. β-CN hydrolysis by either enzyme was always stimulated at the lower pH, yet either inhibited or stimulated by the presence of NaCl, depending mainly on the predominating type of molecular substrate interactions involved at the specific site of cleavage. The potential impact of this proteolytic behavior on cheese quality is discussed.
U2 - 10.1021/jf302890h
DO - 10.1021/jf302890h
M3 - Journal article
C2 - 23110604
SN - 0021-8561
VL - 60
SP - 11421
EP - 11432
JO - Journal of Agricultural and Food Chemistry
JF - Journal of Agricultural and Food Chemistry
IS - 45
ER -