Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.23 (beta-galactosidase)
14,648 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

Human factor VIII/von Willebrand factor protein containing 120 +/- 12 nmol of sialic acid and 135 +/- 13 nmol of galactose/mg of protein was digested with neuraminidase. The affinity of native factor VIII/von Willebrand factor and its asialo form for the hepatic lectin that specifically binds asialoglycoproteins was assessed from in vitro binding experiments. Native factor VIII/von Willebrand factor exhibited negligible affinity while binding of the asialo derivative was comparable to that observed for asialo-alpha1-acid glycoprotein. Incubation of asialo-factor VIII/von Willebrand factor with Streptococcus pneumoniae beta-galactosidase removed only 62% of the galactose but abolished binding to the purified hepatic lectin. When the asialo derivative was incubated with purified beta-D-galactoside alpha2 leads to 6 sialyltransferase and CMP-[14C]NeuAc, only 61% of the galactose incorporated [14C]NeuAc. From the known specificites of these enzymes, it is concluded that galactose residues important in lectin binding are present in a terminal Gal/beta1 leads to 4GlcNAc sequence on asialo-factor VIII/von Willebrand factor. The relative ristocetin-induced platelet aggregating activity of native, asialo-, and agalacto-factor VIII/von Willebrand factor was 100:38:12, respectively, while procoagulant activity was 100:100:103.
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PMID:Carbohydrate on human factor VIII/von Willebrand factor. Impairment of function by removal of specific galactose residues. 10 Apr 92

The activity of neuraminidase in liver and brain from I-cell disease (Mucolipidosis II) was investigated. Neuraminidase activities using two substrates [alpha-L-N-acetylneuraminosyl(2 leads to 3)lactose and alpha-L-N-acetylneuraminosyl(2 leads to 6)lactose] were reduced in the supernatant and sedimentable fractions obtained in isotonic KCl. The activity of beta-D-galactosidase was also reduced in the liver; on the other hand, both neuraminidase fractions were normal, although beta-galactosidase activities were markedly reduced. In view of these results, it is suggested that the defect of neuraminidase is not directly responsible for the primary etiology of I-cell disease.
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PMID:Neuraminidase activity in liver and brain from patients with I-cell disease. 11 36

Thyroxine-binding globulin (TBG), prepared from human serum by an improved purification method, was treated with a mixture of neuraminidase, beta-galactosidase, alpha-mannosidase, and beta-N-aectylglucosaminidase, which resulted in the removal of approximately 86% of saccharides. Purification by thyroxine-Sepharose affinity chromatography gave a homogeneous protein as shown by equilibrium sedimentation and sodium dodecylsulfate-polyacrylamide gel electrophoresis. Amino acid and NH2-terminal sequence analysis indicated that the protein moiety was intact. Deglycosylation had no effect on the stoichiometry of the binding of L-thyroxine as shown by tryptophanyl fluorescence quenching and equilibrium dialysis at pH 8.6 and 25 degrees C. However, the affinity constant for L-thyroxine was reduced from 1.6 X 10(9) M-1 to 0.58 X 10(9) M-1. Analysis of radioimmunoassay data revealed that deglycosylation resulted in a slight decrease of the affinity constant for anti-TBG antibody from 3.9 X 10(10) M-1 to 1.8 X 10(10) M-1. These results suggest that the polypeptide moiety, rather than the heterosaccharides, contains the antigenic determinants. Removal of the majority of the heterosaccharides of TBG has only a minor effect on its immunoreactivity and on the binding of thyroid hormone.
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PMID:Effect of deglycosylation on the binding and immunoreactivity of human thyroxine-binding globulin. 11 1

Two forms of beta-galactosidase from newborn rat epidermis could be separated by DEAE-cellulose chromatography. Both enzymes showed similar enzymic properties. They had a pH optimum around 3.5--4.5 and the optimal temperature of these enzymes was approximately 60 degrees C. They were not affected by divalent cations, ethylenediaminetetraacetic acid(EDTA) and 2-mercaptoethanol(2-ME), while rho-chloromercuribenzoic acid (PCMB) was a strong inhibitor for each enzyme. These enzymes showed the same Km value (1.25 x 10(-4) M) towards 4-methylumbelliferyl-beta-D-galactoside. However they had different isoelectric points at pH 6.3 and 9.0, respectively. Six different forms of beta-galactosidase activity were found by using isoelectric focusing. When the crude extract was incubated with neuraminidase before electrofocusing, the acidic forms of the enzyme were largely lost and converted to more basic forms without loss of the total activity. This finding suggests the glycoprotein nature of newborn rat epidermal beta-galactosidase.
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PMID:Heterogeneity and some properties of beta-galactosidase from newborn rat epidermis. 11 67

Adsorptive endocytosis of alpha-N-acetylglucosaminidase from human urine by isolated rat hepatocytes is inhibited by glycoproteins, polysaccharides and sugars that are known to bind to cell-surface receptors specific for either terminal galactose/N-acetylgalactosamine residues, terminal mannose residues or mannose 6-phosphate residues. Recognition of alpha-N-acetylglucosaminidase by a cell-surface receptor specific for terminal galactose/N-acetylgalactosamine residues is supported by the observations (a) that neuraminidase pretreatment of the enzyme enhances endocytosis, (b) that beta-galactosidase treatment decreases endocytosis and (c) that neuraminidase pretreatment of hepatocytes decreases alpha-N-acetylglucosaminidase endocytosis. Recognition of alpha-N-acetylglucosaminidase via receptors recognizing mannose 6-phosphate residues is lost after treatment of the enzyme with alkaline phosphatase and endoglucosaminidase H. The effect of endoglucosaminidase H supports the view that the mannose 6-phosphate residues reside in N-glycosidically linked oligosaccharide side chains of the high-mannose type. The weak inhibition of endocytosis produced by compounds known to interact with cell-surface receptors specific for mannose residues suggests that this recognition system plays only a minor role in the endocytosis of lysosomal alpha-N-acetylglucosaminidase by hepatocytes.
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PMID:Recognition of human urine alpha-N-acetylglucosaminidase by rat hepatocytes. Involvement of receptors specific for galactose, mannose 6-phosphate and mannose. 11 70

Neuraminidase was assayed in the frozen autopsy tissues from three patients with I-cell disease and an adult patient with cherry-red spots, myoclonus, cerebellar ataxia and beta-galactosidase deficiency. Both diseases showed normal neuraminidase activity toward neuramine lactose and fetuin in cerebral gray matter, liver and kidney. These results suggest that the neuraminidase deficiency is limited only to some tissues and that this biochemical abnormality is not caused by a primary genetic mutation in these diseases.
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PMID:Neuraminidase in mucolipidoses: normal activity in frozen autopsy tissues from three patients with I-cell disease and adult beta-galactosidase deficiency. 11 81

Hybrid cell lines isolated after fusions between Chinese hamster E36 cells and normal human white blood cells were analyzed for human beta-galactosidase isoenzymes and for human chromosomes, especially 3, 12, and 22, the candidates for bearing a beta-galactosidase locus. Results of neuraminidase treatment of the cell lysates and immunological studies showed that in man two structural beta-galactosidase loci are present and can be assigned to chromosomes 3 and 22. No correlation was found between the expression of human beta-galactosidase and the presence of human chromosome 12.
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PMID:Assignment of structural beta-galactosidase loci to human chromosomes 3 and 22. 11 56

Human lymphocyte cultures produced large amounts of interferon after treatment with the enzyme galactose oxidase. Interferon production was detectable as early as 3 h after enzymatic treatment and reached a level of about 10(4) reference units 20 to 24 h later. Galactose oxidase-induced interferon appeared to be immune interferon on the basis of acid lability, lack of neutralization by antibody to leukocyte interferon, and slow kinetics of activation of the cellular antiviral state. Interferon production was inhibited to the same extent (99%) by pretreatment of the cells with beta-galactosidase or with neuraminidase followed by beta-galactosidase, suggesting that the critical event for activation of interferon production is the oxidation of exposed galactose residues on lymphocyte membrane.
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PMID:Enzymatic induction of interferon production by galactose oxidase treatment of human lymphoid cells. 11 35

Two adult siblings with progressive pyramidal and extrapyramidal lesions, and generalized muscle atrophy had a profound deficiency of beta-galactosidase in all the cells and body fluids examined. Neuraminidase activity was normal in fibroblasts. The fused fibroblasts of infantile GMl-gangliosidosis and each of these adult patients had beta-galactosidase activity as expected for the average value in a mixture of equal numbers of parental cells. However, there was a remarkable increase in the activity of beta-galactosidase when the cells from each of these cases were fused with those from the beta-galactosidase-deficient adult with cherry-red spots, cerebellar ataxia, myoclonus and neuraminidase deficiency in fibroblasts. It was concluded that the two siblings represent a new genetic variant (adult type) of GMl-gangliosidosis.
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PMID:Adult type GMl-gangliosidosis: a complementation study on somatic cell hybrids. 12 69


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