Mj. Sousa et Fx. Malcata, PROTEOLYSIS OF OVINE AND CAPRINE CASEINS IN SOLUTION BY ENZYMATIC EXTRACTS FROM FLOWERS OF CYNARA-CARDUNCULUS, Enzyme and microbial technology, 22(5), 1998, pp. 305-314
Primary proteolysis of ovine and caprine Na-caseinate at 30 degrees C
in phosphate buffer at pH 6.5 or 5.5 in the absence of NaCl and at pH
5.2 with 5% (w/v) NaCl by cardosins in aqueous extracts of Cynara card
unculus flowers was investigated using urea-polyacrylamide gel electro
phoresis and reversed-phase high performance liquid chromatography. Ca
prine caseinate underwent more extensive degradation than ovine casein
ate under the same conditions (pH 6.5 and pH 5.5); proteolysis of beta
- and alpha(s)-caseins in ovine and, to a lesser extent, in caprine ca
seinates was reduced in the presence of 5% (w/v) NaCl. Peptide profile
s of the pH 4.6-soluble extract had different patterns throughout ripe
ning arising from the different specificity of cardosins toward ovine
and caprine Na-caseinates. The major cleavage sites in ovine (caprine)
caseinate were Phe105-Met106 (Lys116-Thr117) for kappa-casein, Leu127
-Thr128 and Leu190-Tyr191 (Glu100-Thr101, Leu127-Thr128, Leu136-Pro137
and Leu190-Tyr191) for beta-casein, Phe(23)-Val(24) (Phe(23)-Val(24),
Trp164-Tyr165 and Tyr173-Thr174) for alpha(s1)-casein and Phe88-Tyr89
(Ser9-Ser10, Phe88-Tyr89 and Tyr179-Leu180) for alpha(s2)-casein. (C)
1998 Elsevier Science Inc.