Proteose-Peptone Fraction of Bovine Milk: Lacteum Serum Component 3—A Whey Glycprotein

Abstract

Lacteal serum Component 3 was isolated from both heated and unheated skimmilk. Unlike lacteal serum Components 5 and 8 which exist both in whey and in association with the casein components, Component 3 is found only in the whey protein fraction of skimmilk. Component 3 is characterized by a high content of carbohydrates (≈17.3%) and a low content of aromatic and sulfur-containing amino acids. In veronal buffer, the following physical parameters were determined: D°20,w = 1.8, S°20,w = 3.9, and M̅°W=163,000. In veronal-GU · HCl, they were D°20,w = 1.1, S°20,w = 1.6, and M̅°W=40,800, respectively. A minimum molecular weight, calculated from the limiting amino acid residues, was estimated at 22,000. An isoelectric pH of —3.7 and a partial specific volume of 0.73 were reported for Component 3. © 1970, American Dairy Science Association. All rights reserved.