Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.53 (sialidase)
 2,694 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Carbohydrate-deficient transferrin (CDT) is now considered to be the most sensitive and specific biological marker of alcohol abuse. However, the mechanism by which chronic alcohol consumption causes an elevation of CDT levels in serum is still not understood. Therefore, we fed eight pairs of male rats a nutritionally adequate liquid diet containing either alcohol (36% of energy) or isocaloric dextrose (control) for 4 weeks, after which blood and liver samples were obtained. Serum CDT content in alcohol-treated rats increased by 45% (P < .05) in ethanol-fed animals compared with their corresponding controls. In contrast, in rats fed ethanol, the activities of sialyltransferase (ST), galactosyltransferase (GT), and N-acetylglucosamine transferase (N-AGT), which are glycosyltransferases involved in transferrin carbohydrate side chain synthesis, were diminished by 24% and 40% (P < .05), 23% and 51% (P < .05, .001), and 20% and 26% (P < .05) in total liver homogenates and Golgi fraction (GF) 1, respectively, when expressed as units/100 g body weight. These enzymes were also significantly less active in hepatic GFs 2 and 3. The depression of the transferase activities in ethanol-fed rats appeared to be due, at least in part, to enzyme inactivation by acetaldehyde, whereas ethanol itself was without effect. Similar results were obtained in humans: five alcohol abusers were found to exhibit a 23% decrease in hepatic sialyltransferase and a 41% increase in sialidase activities, respectively, when compared with three nondrinking subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Serum carbohydrate-deficient transferrin: mechanism of increase after chronic alcohol intake. 759 Jun 64

Transferrin is N-glycosylated glycoprotein and plays an important role in iron transport from sites of absorption and storage to sites of utilization. Chronic ethanol alters the normal microheterogeneity pattern of transferrin as a consequence of changes in the sialic acid content. However the underlying basis of this change in sialic acid contents of transferrin in alcohol abuse remains unclear. We have undertaken this study in order to investigate the effects of chronic ethanol in rats with respect to the hepatic rate of (i) transferrin synthesis based on labeled leucine incorporation, (ii) the incorporation of labeled N-acetyl mannosamine (NAM) into sialic acid residues of transferrin, and (iii) roles of specific sialyltransferase and sialidase at hepatic subcellular level. The results showed no significant difference in the incorporation of labeled leucine into transferrin at all levels between the control and ethanol group, whereas the incorporation of NAM into transferrin was significantly decreased by 84% (p < 0.001) both at the whole cell and Golgi level. Thus, the incorporation of labeled NAM relative to the incorporation of labeled leucine into hepatic transferrin was significantly decreased by 86% (p < 0.001) in chronic ethanol-treated animals as compared with the controls both at the whole cell golgi levels. These data are further supported by our finding of concomitant decrease in the activity of beta-galactoside alpha 2,6-sialyltransferase by 58% (p < 0.01) in ethanol-treated rats as compared with control animals.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of chronic ethanol on enzymes regulating sialylation and desialylation of transferrin in rats. 833 87

Serum concentration of carbohydrate-deficient transferrin (cCDT) is used for laboratory diagnosis and follow-up of chronic alcohol abuse. In analyzing by CDTect-RIA (Pharmacia) sera from outpatients with combined pancreas and kidney transplantation and no excessive alcohol consumption, we found above-normal values for cCDT and CDT/transferrin ratios (CDT/Tf) in more than half of the samples. Isoelectric focusing of these samples showed distinct bands of carbohydrate-deficient isotransferrins, supporting the abnormal findings from the CDTect assay. In contrast, diabetics and outpatients who had received only kidney transplants showed normal values for cCDT, CDT/Tf, and isotransferrin patterns. Increased serum Tf, sialidase-producing microorganisms, and immunosuppressive medication were eliminated as causes of these abnormal cCDT and CDT/Tf results. Successful pancreas transplantation leads to hyperinsulinemia and normoglycemia, in contrast to hypoinsulinemia and hyperglycemia in the patients who receive kidney transplants alone. These factors may have pathogenic importance for CDT increase, yielding results falsely interpreted as positive with respect to alcohol abuse in patients with combined pancreas and kidney transplantation.
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PMID:Increased serum concentration of carbohydrate-deficient transferrin in patients with combined pancreas and kidney transplantation. 902 38