Purification and physicochemical characterization of ovine beta-lactoglobulin and alpha-lactalbumin.
Ovine whey proteins were fractionated and studied by using different analytical techniques. Anion-exchange chromatography and reversed-phase high-performance liquid chromatography (HPLC) showed the presence of two fractions of beta-lactoglobulin but only one of alpha-lactalbumin. Gel permeation and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis allowed the calculation of the apparent molecular mass of each component, while HPLC coupled to electrospray ionisation-mass spectrometry (ESI-MS) technique, giving the exact molecular masses, demonstrated the presence of two variants A and B of ovine beta-lactoglobulin. Amino acid compositions of the two variants of beta-lactoglobulin differed only in their His and Tyr contents. Circular dichroism spectroscopy profiles showed pH conformation changes of each component. The thermograms of the different whey protein components showed a higher heat resistance of beta-lactoglobulin A compared to beta-lactoglobulin B at pH 2, and indicated high instability of ovine alpha-lactalbumin at this pH.
Institut National de la Recherche Agronomique, Laboratoire d'Etude des Interactions des Molécules Alimentaires, rue de la Géraudière, B.P. 71627, F-44316 Nantes, France.
Khaled
K
El-Zahar
Mahmoud
M
Sitohy
Michèle
M
Dalgalarrondo
Yvan
Y
Choiset
François
F
Métro
Thomas
T
Haertlé
Jean-Marc
JM
Chobert
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002152:Calorimetry, Differential Scanning; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006863:Hydrogen-Ion Concentration; D007768:Lactalbumin / Q000032:analysis / Q000737:chemistry* / Q000302:isolation & purification; D007782:Lactoglobulins / Q000032:analysis / Q000737:chemistry* / Q000302:isolation & purification; D013058:Mass Spectrometry; D008894:Milk Proteins / Q000032:analysis*; D008970:Molecular Weight; D012756:Sheep; D000067816:Whey Proteins
D000596:Amino Acids; D007782:Lactoglobulins; D008894:Milk Proteins; D000067816:Whey Proteins; D007768:Lactalbumin