title: Influence of high hydrostatic pressure on the proteolysis of beta-lactoglobulin A by trypsin.
abstract: 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.
authors.affiliation: Instituto de Fermentaciones Industriales (CSIC), Juan de la Cierva, 3, 28006 Madrid, Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: Chicón
authors.forename: Josefina
authors.initials: J
authors.lastname: Belloque
authors.forename: Isidra
authors.initials: I
authors.lastname: Recio
authors.forename: Rosina
authors.initials: R
authors.lastname: López-Fandiño
mesh_terms: D000818:Animals; D006868:Hydrolysis; D006874:Hydrostatic Pressure; D007782:Lactoglobulins / Q000378:metabolism*; D008892:Milk / Q000201:enzymology* / Q000378:metabolism; D013997:Time Factors; D014357:Trypsin / Q000378:metabolism*
chemical_list: D007782:Lactoglobulins; D014357:Trypsin