The topography of bovine beta-casein at an oil/water interface as determined from the kinetics of trypsin-catalysed hydrolysis.
The topography of bovine beta-casein at a soya oil/water interface was studied by following the kinetics of the trypsin-catalysed hydrolysis. Tryptic peptides were identified from their amino acid compositions and the kinetics were compared with those obtained from beta-casein in solution. Whereas soluble beta-casein was initially hydrolysed at a number of trypsin-sensitive bonds, the hydrolysis of the protein at the interface was a more ordered event. The crucial initiating step was the cleavage of the N-terminal peptides 1-25 and 1-28 from the molecule. Hydrolysis at other trypsin-sensitive sites could then occur. This suggests that with the exception of the large hydrophilic moiety in the N-terminal region, most of the beta-casein molecule is inaccessible to the proteinase, and lies fairly flat on the oil/water interface. After removal of the N-terminal peptide, the remaining macropeptide can reorientate and other hydrophilic regions become accessible to the proteinase.
Leaver
J
J
Hannah Research Institute, Ayr, Scotland, U.K.
Dalgleish
D G
DG
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002364:Caseins / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D006868:Hydrolysis; D007700:Kinetics; D012995:Solubility; D013024:Soybean Oil / Q000737:chemistry; D014357:Trypsin / Q000378:metabolism*; D014867:Water / Q000737:chemistry
D000596:Amino Acids; D002364:Caseins; D014867:Water; D013024:Soybean Oil; D014357:Trypsin