Proteins of Milk

Whitney, R.McL.

doi:10.1007/978-1-4615-7050-9_3

Cited by 46 publications

(26 citation statements)

References 352 publications

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“…Of the four caseins, aS2-casein accounts for only approximately 10% of the caseins (Whitney, 1988) and the molecule has undergone a high rate of changes during the course of evolution (Holt and Sawyer, 1988). In human, the protein is not present at all (Yamauchi et al, 1981) and in mouse and rat the part of the polypeptide chain containing the cysteines is deleted (Henninghausen et al, 1982;Hobbs and Rosen, 1982).…”

Section: Discussionmentioning

confidence: 99%

Localization of two interchain disulfide bridges in dimers of bovine α_s2‐casein

Rasmussen¹,

Højrup²,

Petersen

1992

European Journal of Biochemistry

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Carboxymethylation of bovine skimmed milk with 14C-labelled iodoacetic acid followed by purification of the a,,-casein dimer showed that all four cysteine residues in the protein are engaged in disulfide linkages. Mass spectrometry and sequence analysis of cystine-containing tryptic peptides revealed the presence of two interchain disulfide bridges in the protein. Sequence analysis of disulfidelinked peptides resulting from an enzymatic cleavage between the bridges demonstrated that the individual chains in the dimers are either aligned in an antiparallel or a parallel orientation. The identity of some of the disulfide-linked peptides was further verified by performic acid oxidation followed by sequence analysis of the resulting peptides.The caseins are the predominant proteins synthesized in the mammary gland and occur in milk as large stable calcium phosphate -protein complexes termed micelles. As well as being the prime source of amino acids, the casein micelle serves as a carrier of calcium phosphate, thus providing the neonate with a source of calcium and phosphate for bone formation. In milk the casein micelles are maintained in a stable colloidal dispersion. However, when the C-terminal part of rc-casein is cleaved off by chymosin, the micelles become insoluble and a coagulation process occurs. In bovine milk the micelles are composed of four caseins aSl-, as,-, p-and rc-casein whose amino acid sequences have been determined at the protein level (Mercier et al., 1971(Mercier et al., , 1973Ribadeau Dumas et al., 1972;Brignon et al., 1977) and at the cDNA level (Stewart et al., 1984(Stewart et al., , 1987.There is no generally accepted model of the micelle although it is believed that the smaller submicelles are used as building blocks (Farrell, 1988). A characteristic feature of the caseins is their high content of phosphorylated seryl residues which are located in specific phosphorylation site motifs (Holt and Sawyer, 1988; Kemp and Pearson, 1990) and are essential for the interaction with inorganic calcium phosphate. The caseins have been divided into two classes according to their sensitivity to precipitation by Ca2+ (Waugh, 1971). a,,-Casein which belongs to the calcium-sensitive group comprises four components previously designated as a,,-, aS3-, as4 and as6-casein (Annan and Manson, 1969). These components have identical amino acid sequences (207 residues) but differ in their phosphate content (Brignon et al., 1976). Of the four caseins only a,,-casein and rc-casein contain cysteines. In JCcasein they are used in multimerization (Talbot and Waugh, 1970) whereas it has been reported that a,,-casein naturally Correspondence to T. E.

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Section: Discussionmentioning

confidence: 99%

Localization of two interchain disulfide bridges in dimers of bovine α_s2‐casein

Rasmussen¹,

Højrup²,

Petersen

1992

European Journal of Biochemistry

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“…There is an asialotetrasaccharide which is found in both bovine colostrum and human milk. But the point of saccharide attachment is not uniform [Eigel et al, 1984;Whitney, 1988;Fiat & Jolles, 1989]. Several reports indicate that multiple saccharide substituents may be linked on a single peptide chain [Doi et al, 1980;.…”

Section: Structure Of Glycomacropeptidementioning

confidence: 99%

“…Several reports indicate that multiple saccharide substituents may be linked on a single peptide chain [Doi et al, 1980;. In contrast to this variability, one phosphate moiety in GMP is always at serine 44 (Ser149 of the κ-casein chain) though non-phosphorylated fractions have been found [Fiat et al, 1981;Eigel et al, 1984;Whitney, 1988;Farrell et al, 2004].…”

Section: Structure Of Glycomacropeptidementioning

confidence: 99%

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Healthy Multifunctional Spectra of Milk Glycoproteins and Their Fragments – a Review Article

Fayed¹

2012

Pol. J. Food Nutr. Sci.

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“…Whey proteins are described as the globular proteins, which are roughly 3.6 nm in diameter, that remain in the milk serum after the precipitation of caseins at pH 4.6 at 20 ºC (Fox & McSweeney, 1998) (Whitney, 1988). Like caseins, whey proteins contain several components: β-lactoglobulin (β-Lg) and α-lactalbumin (α-La).…”

Section: Proteinmentioning

confidence: 99%

The Effects of Microfluidization and Homogenization on the Composition and Structure of Liposomal Aggregates from Whey Buttermilk and Commercial Buttermilk

Nguyen

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The effects of microfluidization and homogenization on the structure of liposomal aggregates from whey buttermilk and commercial buttermilk Tracey Mai T. Nguyen Milk derived ingredients from the production of cheese and butter can be used as vehicles for nutrients. Buttermilk is a nutritious product of milk that comes from the churning of cream into butter. One of the advantages of buttermilk is that it is enriched in milk fat globule components, such as phospholipids and forms emulsions with fat when treated with high shear. The objective of this work was to explore the effects of shear on regular buttermilk and whey buttermilk in terms of liposomal aggregate size and chemical composition. The effects of microfluidization at 2000 psi and homogenization at 2000 psi/500 psi on the particle size distribution of liposomal aggregates between whey buttermilk (WBM) at pH 4.6 and 6.8 and commercial sweet buttermilk (SBM) at pH 4.60 were compared with whey protein isolate (WPI) at pH 4.6. At pH 6.80, WPI and SBM are too soluble in water to measure particle size but WBM is not as soluble. From this investigation, the mean particle diameter of the SBM aggregates at pH 4.6 decreased after the first pass through the microfluidizer and the same is true, after homogenization. SBM aggregates at pH 4.6 had a significantly larger mean particle diameter before treatments in both shear processes compared to WPI at pH 4.6 and WBM at pH 4.6 and WBM at pH 6.8 (p < 0.0001). WPI at pH 4.6 and WBM at both pH showed no significant differences in their mean particle size in both homogenized and microfluidized treatments. WPI and SBM samples resulted in significant particle diameter differences from before to after homogenizing at pH 4.6. SBM at pH 4.6 had significantly larger v average particle diameter than WBM at pH 4.6 (p < 0.0002), WPI at pH 4.6 (p < 0.0002) and WBM at pH 6.8 (p < 0.0045) before microfluidization at pass 0.WBM and WPI across all treatments showed very similar tendencies in small particle size attributes and some similarities in protein composition. In addition, the small aggregate size of WBM is suggested to be influenced by the presence of phospholipids and thus, creating significantly smaller mean particles compared to SBM even before inducing high shear. In contrast, treated and untreated SBM differed from WBM in phospholipid composition in both homogenization and microfluidization techniques.WBM samples contained more phospholipids than SBM, whereas WPI samples contained very low concentrations of phospholipids. Through HPLC analysis, WPI, SBM, and WBM showed different profiling of the phospholipid classes. These differences may be due structural changes of the aggregates from shearing, initial thermal treatments or hydrophobic and/or protein-phospholipid interactions between the aggregates. SBM samples also exhibited different protein profiling than WBM and WPI samples. This study suggests that high shear and presence of phospholipids impact the size distribution of liposomal aggregates through structural...

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Proteins of Milk

Cited by 46 publications

References 352 publications

Localization of two interchain disulfide bridges in dimers of bovine α_s2‐casein

Localization of two interchain disulfide bridges in dimers of bovine α_s2‐casein

Healthy Multifunctional Spectra of Milk Glycoproteins and Their Fragments – a Review Article

The Effects of Microfluidization and Homogenization on the Composition and Structure of Liposomal Aggregates from Whey Buttermilk and Commercial Buttermilk

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Proteins of Milk

Cited by 46 publications

References 352 publications

Localization of two interchain disulfide bridges in dimers of bovine αs2‐casein

Localization of two interchain disulfide bridges in dimers of bovine αs2‐casein

Healthy Multifunctional Spectra of Milk Glycoproteins and Their Fragments – a Review Article

The Effects of Microfluidization and Homogenization on the Composition and Structure of Liposomal Aggregates from Whey Buttermilk and Commercial Buttermilk

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Product

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Localization of two interchain disulfide bridges in dimers of bovine α_s2‐casein

Localization of two interchain disulfide bridges in dimers of bovine α_s2‐casein