Isolation and characterization of an aggregating peptide from a tryptic hydrolysate of whey proteins.
Spontaneous precipitation of a peptide mixture has been observed during the concentration by reverse osmosis of a tryptic hydrolysate of whey protein. The precipitated material collected by centrifugation could not be solubilized by urea, mercaptoethanol, or sodium dodecyl sulfate. However, a complete solubilization of the aggregates was observed when the pH of the solution was lowered to 2.0. Analysis of the insoluble fraction has allowed the identification of beta-lactoglobulin (beta-lg) fragment 1-8 as the major peptide involved in the formation of aggregates. Peptide beta-lg f1-8 accounted for >94% of the peptide content in the precipitate washed twice with distilled water. The investigation of the secondary structure using circular dichroism evidenced that the peptide beta-lg f1-8 isolated from the flocculated peptide mixture is under random coil conformation at acidic and neutral pH and tends to adopt a beta-sheet conformation at basic pH. The findings of this study provide evidence that peptide beta-lg f1-8 forms aggregates via an efficient self-assembly process.
Pouliot
Yves
Y
STELA Dairy Research Center, Institute of Nutraceuticals and Functional Foods (INAF), Université Laval, Quebec City, Quebec, Canada G1V 0A6. Yves.Pouliot@inaf.ulaval.ca
Guy
Marie-Michèle
MM
Tremblay
Mélanie
M
Gaonac'h
Anne-Cécile
AC
Chay Pak Ting
Bertrand P
BP
Gauthier
Sylvie F
SF
Voyer
Normand
N
D011232:Chemical Precipitation; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007782:Lactoglobulins / Q000737:chemistry*; D008894:Milk Proteins / Q000737:chemistry* / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism; D017433:Protein Structure, Secondary; D012995:Solubility; D014357:Trypsin / Q000378:metabolism*
D007782:Lactoglobulins; D008894:Milk Proteins; D010446:Peptide Fragments; D014357:Trypsin