Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.21 (beta-glucosidase)
 3,280 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Rat liver cells obtained by dispersion with collagenase were used to investigate the mode of entry of L-tri-iodothyronine into the cell. 2. The hormone was taken up very rapidly at 23 degrees C; the linear phase of uptake lasted for up to approx. 20 s. 3. A plot of the initial rates of uptake against different concentrations of L-tri-iodothyronine yielded a sigmoidal curve. The Eadie--Hofstee plot (v/[S]2 versus v) yielded two straight lines. The uptake component with an apparent Kt value of 86 +/- 15 pM was designated as system I, and the second uptake component with an apparent Kt of 726 +/- 11 pM as system II. The Hill plot for system I was not linear; the apparent Hill coefficient for system II was calculated to be 2.1.4. Uptake of L-tri-iodothyronine by system I was higher at pH 6.4 than at pH 7.4; system II was relatively insensitive to changes in the pH of the external medium. 5. Both systems exhibited a transition temperature at about 16 degrees C in the Arrhenius plot. The activation energies of the two systems below and above 16 degrees C were 72.8 and 47.7 and 54.4 and 33.1 J/mol respectively. 6. Inhibitors of cellular energy reduced the uptake by system I to a larger extent than that by system II. 7. Replacement of Na+ in the external medium by either K+ or choline led to uptake that followed normal Michaelis--Menten kinetics. 8. Thiol-group-blocking agents reduced the uptake of the hormone by both systems. 9. Treatment of liver cells with beta-glucosidase, Pronase and neuraminidase led to a decrease in the uptake of L-tri-iodothyronine by system I, whereas uptake by system II was decreased after treatment with phospholipase A2, beta-galactosidase. Pronase and neuraminidase. 10. The stereoisomer D-tri-iodothyronine (100--3000 pM) did not affect system I, but uptake by system II decreased with increasing concentration of D-tri-iodothyronine. Reverse L-tri-iodothyronine (2--100 pM) and L-thyroxine (100--3000 pM) did not influence uptake by either system. 11. Under identical conditions of incubation, the uptake of L-tri-iodothyronine was 3.7 times higher than binding to cytosol proteins. The binding was insensitive to metabolic inhibitors. The results suggest that cytosol proteins are not directly involved in the uptake of L-tri-iodothyronine. 12. Plasma-membrane vesicles also take up the hormone rapidly at 23 degrees C. Increasing the osmolarity of the external medium led to a decrease in the uptake of L-tri-iodothyronine by vesicles. 13. Uptake as a function of L-tri-iodothyronine concentration exhibited a sigmoidal curve. The Eadie--Hofstee plot showed two uptake components with apparent Kt values of 96.8 and 1581 pM. 14. The results of our study are consistent with a carrier-mediated translocation of the hormone into the cell.
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PMID:Uptake of L-tri-iodothyronine by isolated rat liver cells. A process partially inhibited by metabolic inhibitors; attempts to distinguish between uptake and binding to intracellular proteins. 4 20

A heat-stable protein was isolated from the spleen of a patient with Gaucher's disease. This protein will activate glucosylceramide beta-glucosidase activity (Ho, M.W. and O'Brien, J.S. (1971) Proc. Natl. Acad. Sci. U.S.A. 68, 2810-2813). When the specificity of this activator was tested using other enzymes and substrates, it was found to activate galactosylceramide beta-galactosidase activity and sphingomyelinase but not GM1 beta-galactosidase or sulfatide sulfatase. The ability to stimulate galactosylceramide beta-galactosidase was optimum at pH 4.6 in the presence of pure phosphatidylserine or other acidic lipids such as sulfatide and phosphatidylinositol. The partially purified activator protein could stimulate galactosylceramide beta-galactosidase activity in brain, liver, leukocytes and cultured fibroblasts. It was not able to stimulate the activity of this enzyme in tissue samples from patients with Krabbe's disease, demonstrating that it was acting on galactosylceramide beta-galactosidase and not GM1 beta-galactosidase. It was slowly denatured by treatment with Pronase, reaching 16% of starting levels after 24 h at 50 degrees C. Attempts to separate the abilities of this activator preparation to stimulate several lysosomal hydrolases by column chromatography were not successful.
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PMID:A protein activator of galactosylceramide beta-galactosidase. 712 30

When cells of the slime mould Dictyostelium discoideum are allowed to starve in the presence of alpha-chymotrypsin, they are blocked in development at the stage where tight aggregates form tips. Analysis of developmentally regulated enzymes has shown that alpha-mannosidase, beta-N-acetylglucosaminidase, threonine deaminase, tyrosine aminotransferase, beta-glucosidase and the carbohydrate-binding protein discoidin are unaffected, but enzymes that show an increase in specific activity during post-aggregative development, namely glycogen phosphorylase, UDP-glucose pyrophosphorylase, UDP-galactose 4-epimerase, UDP-galactose polysaccharide transferase and alkaline phosphatase, did not show the characteristic increase when development was blocked by alpha-chymotrypsin. Recovery of cells from the effects of alpha-chymotrypsin was accompanied by the formation of fruiting bodies and a concomitant increase in the specific activity of UDP-glucose pyrophosphorylase. Uptake or efflux of 45Ca2+ was not altered in the presence of alpha-chymotrypsin. Cells allowed to develop in alpha-chymotrypsin, or treated with the enzyme for 15 min, had a markedly reduced ability to bind cyclic AMP with low affinity; high-affinity binding was unaffected. Pronase had a similar effect on cyclic AMP binding, but trypsin, which does not alter developmental processes, has no effect on cyclic AMP binding to D. discoideum cells.
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PMID:Developmentally regulated enzymes and cyclic AMP-binding sites in Dictyostelium discoideum cells blocked during development by alpha-chymotrypsin. 715 Feb 39