Ot-Lactalbumin

Protein Caseins /1-Lactoglobulin ot-Lactalbumin Serum albumin IgG... 

The enzymes shown in Figure 13.13 participate in mammary gland in the synthesis of lactose in milk. Lactose is formed from UDP-Gal plus glucose by lactose synthase, in the presence of the protein ot-lactalbumin. The endergonic synthesis of UDP-Gal in this tissue proceeds smoothly... 

The common form of the enzyme contains a single polypeptide subunit. The presence of an additional subunit, ot-lactalbumin, changes the specificity of the enzyme so that lactose is synthesized instead. 

This modified enzyme is lactose synthase. Synthesis of ot-lactalbumin is activated hormonally in mothers shortly after giving birth. The ot-lactalbumin protein combines with preexisting galactosyltransferase, changes its specificity, and activates the large amount of lactose synthesis needed for milk production. 

Severe heat treatments, especially >80°C, adversely affect the rennet coagulation of milk. Although changes in calcium phosphate equilibria are contributory factors, complexation of /3-lactoglobulin and/or ot-lactalbumin with x-casein via intermolecular disulfide bond formation is the principal factor responsible (see Fox, 1988). Most authors agree that the primary and, especially, the seconday (nonenzymatic) phase of rennet coagulation are adversely affected by severe heat treatments, as is the strength of the... 

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