Proteolysis of Ovine and Caprine Caseins in Solution by Enzymatic Extracts from Flowers of Cynara cardunculus

NaCl concentrations above 5% decrease proteolysis of caseins.

“but NaCl concentrations above 5% decreased proteolysis of caseins [48,55]”

In ovine and caprine caseinates, β-caseins are cleaved at both Leu127-Thr128 and Leu190-Tyr191, but in caprine caseinate the bonds Glu100-Thr101 and Leu136-Pro137 are also broken down.

“In ovine and caprine caseinates, β-caseins (i.e.β 1 -and β 2 -casein, which are two variants that differ in their level of phosphorylation, 6 and 5, respectively) are cleaved at both Leu 127 -Thr 128 and Leu 190 -Tyr 191 , but in caprine caseinate the bonds Glu 100 -Thr 101 and Leu 136 -Pro 137 are also broken down [55] (Fig. 1b).”

The bond in ovine and caprine αs1-casein most labile to the action of proteinases from C. cardunculus is Phe23-Val24, which produces a set of bands of higher electrophoretic mobility than αs1-casein, corresponding to bovine αs1-I-casein (f24-199).

“The bond in ovine and caprine α s1 -casein most labile to the action of proteinases from C. cardunculus is Phe 23 -Val 24 , which produces a set of bands of higher electrophoretic mobility than α s1 -casein, thus corresponding to bovine α s1 -I-casein (i.e.f24-199) [55].”

The major cleavage site of bovine and ovine κ-casein is Phe105-Met106, whereas caprine κ-casein is preferentially cleaved at Lys116-Thr117.

“The major cleavage site of bovine [31] and ovine κ-casein is Phe 105 -Met 106 , whereas caprine κ-casein is preferentially cleaved at Lys 116 -Thr 117 [55] (Fig. 1a).”

The bond Tyr95-Leu96 is also cleaved in bovine αs2-casein, whereas the bonds Ser9-Ser10 and Tyr179-Leu180 are cleaved in caprine caseinate as well.

“The bond Tyr 95 -Leu 96 was also cleaved in bovine α s2 -casein [32], whereas the bonds Ser 9 -Ser 10 and Tyr 179 -Leu 180 were cleaved in caprine caseinate as well [55].”

αs2-casein is cleaved at Phe88-Tyr89 in bovine, ovine and caprine caseinates.

“Finally, α s2 -casein was cleaved at Phe 88 -Tyr 89 in bovine [32], ovine and caprine caseinates [55] (Fig. 1d).”

Comparison of results suggests that the bonds in pure caseins (or in sodium caseinate) most susceptible to cardosins A and B are Leu190-Tyr191 and Leu127-Thr128 in β-casein, and Phe23-Val24 and Trp164-Tyr165 in αs1-casein.

“However, comparison of the results reported by Ramalho-Santos et al. [38,39], by Sousa and Malcata [55], and by Silva and Malcata [46] suggests that the bonds in pure caseins (or in sodium caseinate, for that matter) most susceptible to cardosins A and B are Leu 190 -Tyr 191 and Leu 127 -Thr 128 in β-casein (Fig. 1b), and Phe 23 -Val 24 and Trp 164 -Tyr 165 in α s1 -casein (Fig. 1c).”

Caprine caseinate undergoes more extensive proteolysis than ovine caseinate under similar conditions (pH 6.5 and pH 5.5).

“Caprine caseinate underwent more extensive proteolysis than the ovine one, under similar conditions (i.e.pH 6.5 and pH 5.5); proteolysis of β-and α s -caseins in ovine and, to a lesser extent, in caprine caseinates was reduced in the presence of 5% NaCl [55].”

Proteolysis of β- and αs-caseins in ovine and, to a lesser extent, in caprine caseinates is reduced in the presence of 5% NaCl.

“Caprine caseinate underwent more extensive proteolysis than the ovine one, under similar conditions (i.e.pH 6.5 and pH 5.5); proteolysis of β-and α s -caseins in ovine and, to a lesser extent, in caprine caseinates was reduced in the presence of 5% NaCl [55].”