ß1,4 Galactosyltransferase (GT) is the enzymatic subunit of lactose synthase. It is a glycoprotein with a molecular weight varying from 35-60 kDa, depending upon the amount of glycosylation and the degree of proteolytic degradation. ß1,4 Galactosyltransferase in milk is proteolytically clipped removing the cytoplasmic and transmembrane domains. The GT found in milk has a molecular weight of 35-45 kDa. Without the presence of -lactalbumin, the enzyme functions in the Golgi during glycoprotein biosynthesis to add galactose to oligosaccharides with terminal -acetylglucosamine residues in a ß1-->4 linkage. The GT transfers galactose from the donor, UDP-galactose, to the terminal -acetylglucosamine (GlcNAc) acceptor on the oligosaccharise complex of glycosylated proteins. Galactosyltransferase is found in most tissues of the body. It is only found on the inner surface of the Golgi apparatus.
Lactose cannot diffuse out of the Golgi and secretory vesicles, so water is drawn into the vesicles to balance the osmotic pressure. Since lactose synthase is necessary for production of lactose and the subsequent movement of water into the mammary secretory vesicles, it is critical in the lactational control and secretion of milk. The substrates for lactose synthase do not appear to be limiting since results of many experiments indicate that infusion of glucose, increasing blood glucose, does not increase milk production. Addition of more than 0.5 mg/ml glucose (low levels) to dispersed mammary cells also does not increase milk production. There is a suggestion that glucose transport across the plasma membrane may be limiting, but this is inconclusive. The expression of the glucose transporter is not up-regulated in cattle when exogenous growth hormone is administered. This suggests that glucose transport across the plasma membrane is not normally a limiting factor in milk production. The glucose transporter from the cell cytoplasm to the Golgi has a very large capacity and it seems unlikely that glucose transport across the Golgi membrane is limiting.
Dehydration Synthesis and Hydrolysis – Practice …
This is a good name for it.
It's a synthesis, or creation, of something new, in this case, a new disaccharide.
And we essentially pulled water off of these two glucoses, so we dehydrated it.
So there you have it, a dehydration synthesis.