Sialyltransferases serum

Sialyltransferases can be solubilized from their subcellular site by using detergents, and be purified by affinity chromatography on, for example, CDP-6-aminohexanol-agarose,267 as already described. Solubilization of frog- and rat-liver sialyltransferases by means of Triton X-100 has been described.27 Soluble sialyltransferase occurs in colostrum, and is also present in small quantities in normal blood-serum. From the latter source, the enzyme was purified 300-fold by poly (acrylamide) gel-electrophoresis.2 ... 

In the case of rat and human-breast cancer, an increase in serum-sialyltransferase activity is considered to be the consequence of both increased production and release, the latter perhaps through cell-surface shedding of the enzyme from the metastasizing, mammary-tumor cells.290 Accordingly, release of large amounts of sialyltransferase from hepatoma cell-lines derived from patients having hepatocellular carcinoma was observed, in contrast to cell lines derived from nomial human-liver.291 An increased level of sialyltransferase has been observed in regenerating rat-liver.292... 

Table III. Comparison of Serum-induced ODC Activity with CMP-NeuAc lactosylceramide Sialyltransferase Activity in Various Cell Lines...

The sialyltransferases are membrane-bound proteins located in the endoplasmic reticulum (ER) and in the Golgi apparatus. Information about their sequence homology is limited, but they do appear to share a common topography [35]. A catalytic domain resides at the C-terminus followed by an N-terminal segment that anchors the enzyme into the ER or Golgi membrane. Soluble, catalytically active sialyltransferases that lack the anchor segment have been isolated from milk, serum, and other body fluids, suggesting that this N-terminal anchor is not necessary for the enzyme to retain catalytic activity. However, the ability to obtain from natural sources quantities of most sialyltransferases that would be needed for synthesis applications is hampered by low tissue concentrations and difficult purifications. 

Both in Alzheimer s disease and older Down s syndrome subjects, a decrease in serum sialyltransferase activity was observed [1099,1100]. This was found to affect only the a-2,3-sialyltransferase, also leading to a decrease of a-2,3-linked sialic acid in serum glycoproteins. It can only be assumed at present that this observation mirrors reduced activity of sialyltransferase and decreased sialoglycoconjugate biosynthesis in neuronal tissue subjected to these degenerative diseases. Serum sialyltransferase may thus be an early biochemical marker of neurodegeneration. 

Kaplan HA, Woloski BM, Heilman M, Jamieson JC (1983) Studies on the effect of inflammation on rat liver and serum sialyltransferase. Evidence that inflammation causes release of Gal beta 1 leads to 4GlcNAc alpha 2 leads to 6 sialyltransferase from liver. J Biol Chem 258 11505-11509... 

Incubate a solution of polymer 25 (22 mg, approx 20 pmol of substrate), cytidine-5 -monophospho-N-acetyl neuraminic acid (CMP-NeuAc, Sigma C 8271) (15 mg, 24.4 xmol), a-(2—>3)-sialyltransferase (from rat liver, Sigma S 2769) (0.3 unit), bovine serum albumin (BSA, 4 mg), and calf intestinal alkaline phosphatase (CIAP, Sigma P 7923) (20 unit) in 50 mM sodium cacodylate buffer (pH 7.4, 2.0 mL) containing manganese(II) chloride (0.62 mg) and Triton CF-54 (10 xL) at 37°C for 72 h. 

Soluble sialyltransferase activity has often been measured in the serum of tumour patients and significant elevation detected (Bernacki and Kim 1977, Ganzinger 1977, Henderson and Kessel 1977, Coombes et al 1978, Ip and Dao... 

Dijak, W. V., Lasthius, A., and van den Eijnden, D. H., 1979, Glycoprotein biosynthesis in calf kidney. Glycoprotein sialyltransferase activities towards serum glycoproteins and calf Tamm-Horsfall glycoprotein, Biochim. Biophys. Acta 584 129-142. 

Fraser, I. H., Coolbear, T., Sarkar, M., and Mookerjea, S., 1984, Increase of sialyltransferase activity in the serum and liver of inflamed rats, Biochim. Biophys. Acta 799 102-105. 

Hudgin, R. L., and Schachter, H., 1971, Porcine sugar nucleotide glycoprotein glycosyl-transferases I. Blood serum and liver sialyltransferase. Can. J. Biochem. 49 829-837. 

---