Blood serum albumin

In blood, BSA serves various functions but it is probably of little significance in bovine milk, although it does bind metals and fatty acids the latter characteristic may enable it to stimulate lipase activity. 

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The compound is a drug for the treatment of rheumatoid arthritis. The mode of transport of this drug in the body involves the exchange of thiomalate ligands in vivo and the binding of Au(I) to -SH and S—S units of proteins, such as blood serum albumin. 

The lactoglobulin fraction consists mainly of immunoglobulins (Ig), especially IgGj, with lesser amounts of IgG2, IgA and IgM (section 4.10). The lactalbumin fraction of bovine milk contains three main proteins, / -lactoglobulin (j8-lg), a-lactalbumin (a-la) and blood serum albumin (BSA), which represent approximately 50, 20 and 10% of total whey protein, respectively, and trace amounts of several other proteins, notably lactotrans-ferrin, serotransferrin and several enzymes. The whey proteins of sheep, goat... 

Classically, lipases hydrolyse ester bonds in emulsified esters, i.e. at a water/oil interface, although some may have limited activity on soluble esters they are usually activated by blood serum albumin and Ca2 + which bind free fatty acids, which are inhibitory. Little lipolysis normally occurs in... 

The proteins of milk fall into several classes of polypeptide chains. These have been delineated most completely in bovine milk, and a system of nonmenclature has been developed for them (Chapter 3 Eigel et al. 1984). One group, called caseins, consists of four kinds of polypeptides asr, as2-. and 3-, and k- with some genetic variants, post translational modifications, and products of proteolysis. Almost all of the caseins are associated with calcium and phosphate in micelles 20-300 fim in diameter (see Chapter 9). The other milk proteins, called whey proteins, are a diverse group including /3-lactoglobulin, a-lactalbumin, blood serum albumin, and immunoglobulins (Chapter 3). Almost all... 

Bovine Serum Albumin. Since Polis et al. (1950) crystallized bovine serum albumin from whey and demonstrated that it was identical in all properties investigated to blood serum albumin, except in its electrophoretic behavior at pH 4.0, very little work has been done on this protein as isolated from milk. However, much work has been done on the protein isolated from bovine blood plasma. There is considerable evidence that serum albumin is heterogeneous. For example, Spencer and King (1971) have demonstrated several protein bands by electrophoretic focusing, with two major isoelectric components differing by one unit of charge. The chemical nature of this difference is not known. 

Proteins are classified into two types according to their composiCioii Simple proteins, such an blood serum albumin, are those that yield only amino acids on hydrolysia. Conjugated proteins, which are much more common than simple proteins, yield other compimnds such as caibohydratM. fats, or nucleic acids in addition to amino acids on hydrofyaia. 

FIGURE 7.3. Mass spectrum of human blood serum albumin in linear mode after in vitro incubation with 0.1 mg/ml RVX at 37° C for 1 h. 

Blood serum albumin (horse), based on per cent of sulphur present,... 

Normal bovine milk contains a low level of blood serum albumin (BSA) (0.1-0.4gl 0.3-1.0% of total N), presumably as a result of leakage from blood. BSA is quite a large molecule (molecular mass c. 66kDa 582 amino acids) its amino acid sequence is known. The molecules contain 17 disulphides and one sulphydryl. All the disulphides involve cysteines that are relatively close together in the polypeptide chain, which is therefore organized in a series of relatively short loops, some of which are shorter than others (Figure 4.27). The molecule is elliptical in shape and is divided into three domains. 

P/litre in cows milk) is distributed between more than 50 different compounds, both organic and inorganic. Most abundant and important of these are the casein phosphoproteins, calcium phosphates and the phospholipids. Other phosphorus compounds, present in much smaller quantities, are vitamins, various nucleic acids, enzymes, sugar phosphates and proteose peptones (phosphoglyco-peptides). Non-phosphorus compounds present at low levels include blood serum albumin, immune globulins, lactoferrin and ceruloplasmin. 

All this led Mulder to the formula C400H620N100O120P1S1 for two of his proteins, and the same for the third, blood serum albumin, but with one more sulphur atom. Now, since no compound can contain less than one atom of any element (unless it is not there at all), this sets a lower limit for the number of atoms in a molecule, and thus for its minimum molecular weight, which for Mulder s three proteins comes out at about 14,400. It is the minimum molecular weight, because the analysis delivers only the proportions of the constituent elements, the true value possibly being 28,800 or 43,200 and so on—assuredly, in any event, a... 

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