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)

Based on reports that ethanol can decrease the level of sialic acid (SA) (neuraminic acid) in several tissues, we tested the hypothesis that ethanol promotes SA cleavage by enhancing the activity of sialidases (neuraminidases). We also investigated whether brain and liver sialidases have the same response to ethanol and gangliosides, especially since our prior studies have demonstrated that gangliosides could antagonize ethanol-induced behavior. Experiments were conducted on homogenates of brain and liver and of liver slices of adult rats. In liver slices, cleavage of SA did not fall in proportion to the ethanol-induced inhibition of sialidase; in fact, at 0.1 M ethanol, free SA increased, even though sialidase was inhibited. Brain sialidase activity on endogenous sialoglycoconjugates was much more resistant to ethanol than liver sialidase and was fully active even in concentrations as high as 1 M. When gangliosides were incubated with liver slices in the absence of ethanol, sialidase was markedly stimulated. The ethanol-induced inhibition of sialdase in liver slices was mimicked by sorbitol, suggesting that the inhibition may be caused by a shift in redox state as a result of increased NADH. The ethanol metabolite, acetaldehyde, does not seem to be a factor, because sialidase inhibition still occurred when slices were incubated with ethanol containing pyrazole. The results indicate that ethanol promotes the accumulation of free SA in liver without stimulating sialdase; our other work suggests that the cause is an increase in accessibility to sialoglycoconjugates rather than decreased utilization of SA. Brain and liver sialidases clearly respond differently to both ethanol and gangliosides.
 ...
PMID:Differences in susceptibility of rat liver and brain sialidases to ethanol and gangliosides. 261 98

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)
 ...
PMID:Serum carbohydrate-deficient transferrin: mechanism of increase after chronic alcohol intake. 759 Jun 64