Sialic acids serum

Mrochek, J. E., Dinsmore, S. R., Tormey, D. C., and Waalkes, T. P., Protein-bound carbohydrates in breast cancer, liquid-chromatographic analysis for mannose, galactose, fucose, and sialic acid in serum, Clin. Chem., 22, 1516, 1976. 

C5-derived peptide in serum. This molecule lacks anaphylatoxin activity (i.e. it cannot cause smooth muscle contraction), and its ability to cause che-motaxis in neutrophils is about 10-20 times lower than that of C5a. However, human serum also contains a heat-stable, anionic protein termed co-chemotaxin (relative molecular mass = 60 kDa), which acts in a concentration-dependent manner to permit C5a des Arg to act as a chemoattractant for neutrophils. Thus, C5a des Arg plus cochemotaxin working together probably account for most of the neutrophil chemoattractant activity in vivo following complement activation. The mechanism of action of cochemotaxin is unknown, but it may form a physical complex by attaching to a sialic acid residue on the oligosaccharide chain of C5a des Arg. Deglycosylation of C5a des Arg increases its chemoattractant activity more than 10-fold, and its dependency upon cochemotaxin is decreased. 

The latter approach has been followed in our laboratory. For instance, in studies related to the synthesis of potent multivalent sialoside inhibitors of influenza virus hemagglutinin [34], it became of interest to evaluate the immunogenicity of neoglycoproteins containing sialosides as sole immunodominant hapten. To this end, acetochloroneuraminic acid (1) was transformed into allyl glycoside 2 (Scheme 1) which upon reductive ozonolysis afforded aldehyde 3 in excellent overall yields [35], Reductive amination of 3 to bovine serum albumin (BSA) and tetanus toxoid provided immunogenic vaccines from which specific rabbit IgG anti-sialic acid antibodies were obtained [36]. In order... 

There is some evidence for the occurrence of a glycolyl group at 0-4 of Neu5Ac in serum and submandibular-gland glycoproteins from the horse, based on biosynthetic studies with radioactive precursors,33 and chemical and t.l.c. analysis of the sialic acid ester groups.74... 

The synthesis and catabolism of Neu5Ac and its derivatives seem to be rigidly controlled, as may be delineated from the low concentrations of sialic acid observed in tissues, serum, and urine (see Section H). 

N-Acylneuraminate-9(7)-0-acetyltransferase seems to be widespread in Nature, as sialic acids O-acetylated in the side chain are found in many animal species, including man (see Section II). However, enzyme activity has thus far been measured only in bovine, submandibular gland and in bovine serum. The 4-O-acetyltransferase appears... 

These studies demonstrating a protective effect of sialic acid residues on serum glycoproteins provide an explanation for earlier, conflicting observations about the biological effect of, for example, desialylated erythropoietin, which stimulates erythropoiesis only after direct application to bone-marrow cell-cultures, and not after injection into the blood stream.469 In the latter experiment, only the native, sialylated hormone was active. Rapid clearance and inactivation of follicle-stimulating hormone,470 or interferon,471 after treatment with sialidase may be explained by uptake into liver cells. 

Sialic acid seems to be involved not only in regulation of the lifetime of soluble, serum glycoproteins but also of mammalian blood-cells. It was observed by Woodruff and Gesner474 that desialylated lymphocytes are reversibly trapped in liver they recirculate to the blood stream after about 24 h. This phenomenon was confinned with Listeria-specific, mouse T lymphocytes, which accumulated in the liver for one day, in contrast to the control cells.60 Reappearance of these cells in the circulation after one day may be explained by re-sialylation of their membrane glycoconjugates. This time period is in the range observed for the turnover of sialic acid in cell membranes, lasting, for example, for 33 h in rat-liver hepatocytes.475... 

Waters PJ, Lewry E, PennockCA (1992) Measurement of sialic acid in serum and urine clinical applications and limitations. Ann Clin Biochem 29 625-637... 

In all known types of CDG-I it has been observed that due to the loss of sialic acid residues, in addition to tetrasialo-transferrin, more or less pronounced di- and asialo-transferrin bands appear, which are evoked by the loss of either one or both complete oligosaccharide chains (Fig. 4.5.3, lanes 2-4). In contrast to CDG-I, changes in the charge of serum transferrin of most known CDG-II types are due to shortening of the oligosaccharide moieties (Fig. 4.5.3, lanes 5-7). 

Fig. 4.5.3 IEF patterns of serum transferrin. Sera from a control (lane 1), three CDG-I (CDG-Ia, CDG-Ic and CDG-Id lanes 2-4) and three CDG-II patients (CDG- , CDG-IId and CDG-IIx lanes 5-7) were analysed by IEF. In case of a control person, the main form of the protein carries four negatively charged sialic acid residues, even though small amounts of penta- and trisialo-transferrin are detectable. Additional disialo- and asialotransferrin forms indicate CDG-type I (left side). In some cases of CDG type II, additional trisialo- and monosialotransferrin forms may occur, which are due to the loss of either one or three sialic acid residues (right side). Isoforms of transferrin that are independent of a pathological phenotype and that cause double bands in IEF are visible in lanes 4 and 6. CDG-IIx indicates a transferrin pattern that is caused by a so far unknown molecular defect from the CDG-II type...

Fig. 4.5.4 Identification of mutations in the transferrin protein by neuraminidase treatment. Unusual patterns in the IEF of serum transferrin might lead to pitfalls in CDG diagnostics. These varying patterns are often due to mutations of charged amino acids in the protein backbone of the transferrin molecule, which might lead, for example, to an accumulation of trisialo transferrin bands (lane 3, indicated by a question mark). Further investigations are carried out by cleaving off charged sialic acid monosaccharide moieties from transferrin-linked oligosaccharides by neuraminidase treatment, followed by IEF and transferrin antibody staining. In the case of protein mutations, additional bands below (lane 4) or above (not shown) the desialylated transferrin form appear...

Fig. 4.5.10 Analysis of core-1 mucin type -linked glycans derived from apolipoprotein C-III (ApoC-III). Serum-derived ApoC-III from a control (lane 1, left) and a CDG-IIx patient (lane 2, right) was investigated by IEF followed by antibody staining with a polyclonal rabbit-a-human ApoC-III antibody. ApoC-IIfi ApoC-IIEand ApoC-III0 indicate the variability in the amount of sialic acid residues linked to ApoC-III...

Cells were grown in RPMI medium plus 5 % fetal bovine serum in 1 mL total volume as described in Materials and Methods. At 24-hr intervals the cells were counted in a Coulter counter. Control cells 0, cells from cultures containing 1000 lU/mL mouse fibroblast interferon , cells from cultures containing bovine brain gangliosides at a concentration corresponding to 35 p.M sialic acid , cells from cultures containing both interferon (1000 IU/mL) and gangliosides (35 p.M sialic acid). 

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