Influence of high hydrostatic pressure on the proteolysis of beta-lactoglobulin A by trypsin.
This work describes the effect of the hydrolysis time and pressure (0.1-400 MPa) on the proteolysis of beta-lactoglobulin A (beta-lg A) with trypsin, either conducting hydrolysis of beta-lg under pressure or hydrolysing beta-lg that was previously pressure treated. Pressurisation, before or during enzyme treatments, enhanced tryptic hydrolysis of beta-lg. Trypsin degraded pressure-modified beta-lg and pressure-induced beta-lg aggregates, favouring proteolysis to the intermediate degradation products: (Val(15)-Arg(40)), (Val(41)-Lys(69))S-S(Leu(149)-Ile(162)) and (Val(41)-Lys(70))S-S(Leu(149)-Ile(162)). These were further cleaved at the later stages of proteolysis to yield: (Val(15)-Tyr(20)), (Ser(21)-Arg(40)), (Val(41)-Tyr(60)), (Trp(61)-Lys(69))S-S(Leu(149)-Ile(162)) and (Trp(61)-Lys(70))S-S(Leu(149)-Ile(162)). Particularly, in the tryptic hydrolysates of pre-pressurized beta-lg, two other fragments linked by disulphide bonds: (Lys(101)-Arg(124))S-S(Leu(149)-Ile(162)) and (Tyr(102)-Arg(124))S-S(Leu(149)-Ile(162)), were found. These corresponded to rearrangement products induced by SH/SS exchange between the free thiol group of Cys(121) and Cys(160), that normally forms the disulphide bond Cys(66)-Cys(160). In the light of these results, structural modifications of beta-lg under high pressure are discussed.
Chicón
Rosa
R
Instituto de Fermentaciones Industriales (CSIC), Juan de la Cierva, 3, 28006 Madrid, Spain.
Belloque
Josefina
J
Recio
Isidra
I
López-Fandiño
Rosina
R
D000818:Animals; D006868:Hydrolysis; D006874:Hydrostatic Pressure; D007782:Lactoglobulins / Q000378:metabolism*; D008892:Milk / Q000201:enzymology* / Q000378:metabolism; D013997:Time Factors; D014357:Trypsin / Q000378:metabolism*
D007782:Lactoglobulins; D014357:Trypsin