Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.108 (lactase)
 2,133 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Unsubstituted naphthyl substrates were found to be superior to substituted naphthyl, indolyl and hydroxyquinoline substrates for the histochemical demonstration of alpha-mannosidase, alpha-galactosidase, hetero-beta-glycosidase, glucoamylase and sucraseisomaltase, equivalent for beta-N-acetylglucosaminidase and lactase-beta-glucosidase, and inferior for beta-glucuronidase and acid beta-galatosidase. Aldehyde fixation is necessary for the localization of lysosomal glycosidases with naphthyl substrates. 1-naphthyl substrates are suitable for the detection of acid glycosidases in lysosomes and hetero-beta-glysocidase in the cytoplasm of animal cells, and 2-naphthyl substrates can be employed for the demonstration of microvillous glycosidases and for the evaluation of the total activity of soluble glycosidases with semipermeable membranes. When naphthyl substrates are used coupling should be carried out simultaneously and hexazotized pararosaniline is the coupling reagent of choice.
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PMID:Localization of glycoidases with naphthyl substrates. 5 19

A method for the histochemical demonstration of "hetero-beta-galactosidase" was elaborated. The enzyme is demonstrated in cryostat sections by the semipermeable membrane technique. Pairs of membranes--one pre-washed in saline--are used. The most sensitive method is post-coupling demonstration with 6-Br-2-naphthyl-beta-D-glucoside. The incubation time must be short, to avoid diffusion. The method allows cellular localization. The method with alpha-naphthyl-beta-D-glucoside and hexazonium-p-rosaniline is less sensitive, but localization is better. Indigogenic methods are the least sensitive. The enzyme is localized in the supranuclear zone of differentiated enterocytes of the human, monkey and rabbit small intestine, with maximum activity in the jejunum. The activity of the enzyme is low in patients with coeliac sprue, in the active phase of the disease. In isolated lactase deficiency it is normal. In the kidney, the enzyme is localized chiefly in the cytoplasm of the proximal tubule cells.
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PMID:Demonstration of "hetero-beta-galactosidase" "in situ". 9 37

1. Three fractions of beta-galactosidase activity from the rat small-intestinal mucosa were separated chromatographically. Two of these fractions had an acid pH optimum at 3-4, and the third one had a more neutral pH optimum at 5.7. 2. The two ;acid' beta-galactosidase fractions had considerably lower K(m) values for hetero beta-galactosides than for lactose. The V(max.) values were similar for all the substrates used (lactose, phenyl beta-galactoside, o-nitrophenyl beta-galactoside, p-nitrophenyl beta-galactoside and 6-bromo-2-naphthyl beta-galactoside). No difference could be detected between the two ;acid' fractions with respect to their enzymic properties (pH optimum, K(m) for the different substrates, K(i) for lactose as an inhibitor of the hydrolysis of hetero beta-galactosides, K(i) for phenyl beta-galactoside as an inhibitor of the hydrolysis of lactose, and relative V(max.) for the hydrolysis of different substrates). These two fractions probably represent different forms of the same enzyme. 3. The ;neutral' fraction had similar K(m) values for all the substrates hydrolysed, but with lactose as substrate the V(max.) was much higher than with the hetero beta-galactosides. This fraction did not split phenyl beta-galactoside or 6-bromo-2-naphthyl beta-galactoside at a measurable rate. 4. Lactose was a competitive inhibitor of the hetero beta-galactosidase activities of all the three fractions, and K(i) for lactose as an inhibitor in each case was the same as K(m) for the lactase activity. Phenyl beta-galactoside was a competitive inhibitor of the lactase activity of all the three fractions. These facts strongly indicate that in all the three fractions lactose is hydrolysed by the same active sites as the hetero beta-galactosides. 5. Human serum albumin stabilized the separated enzymes against inactivation by freezing and thawing.
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PMID:Rat small-intestinal beta-galactosidases. Kinetic studies with three separated fractions. 572 84

Sucrase-isomaltase (SI), trehalase (T) and lactase-beta-glucosidase (LG) activities were assessed histochemically in samples of colorectal adenomas (11 tubular, 12 tubulovillous, 10 villous) and 30 adenocarcinomas obtained by biopsy during colonoscopy or from specimens removed by surgical intervention. Small samples of tumor tissue, tissue of the transitional zone and of macroscopically normal mucosa were quenched in heptan cooled in an acetone-dry ice mixture. Cryostat sections, transferred to non-precooled slides and in some cases to semipermeable membranes, were dried and subjected to the histochemical reactions for SI, T and LG. Sucrose, 2-naphthyl, 6-Br-2-naphthyl, and 5-Br-4-Cl-3-indoxyl alpha-D-glucosides, trehalose, and 5-Br-4-Cl-3-indoxyl-beta-D-fucoside were used as substrates. Sections of jejunal biopsies with normal activities of brush border glycosidases were used as controls. From samples of 5 adenomas, 5 adenocarcinomas and collected rests of jejunal biopsies with a normal finding 10% (w/vol) homogenates in 2% Triton X-100 were prepared. Homogenates were frozen and thawed 3 times and their supernatants subjected to isoelectric focusing on polyacrylamide gel plates. Zymograms were developed with the same methods as for the detection of alpha-glucosidases in sections. In no colorectal tumor LG was present. SI was found in 70% adenocarcinomas, 50% villous, 25% tubulovillous and 19% tubular adenomas when the method with sucrose, glucose oxidase-peroxidase and 3,3'-diaminobenzidine was used. Hardly discernible traces of activity were found in tumors with azo-coupling reactions applied at pH 5, 6 and 6.5. No reaction was detected with the indigogenic method applied at pH above 6.0. However, jejunal biopsies displayed very strong reactions confined to the brush border of enterocytes under the same conditions. A strongly positive reaction was seen in 7 of 12 tumors investigated recently when the indigogenic reaction was applied at pH below 6.0 (particularly at pH 5.0). In this case the deposition of indigo was due to membrane and lysosomal alpha-glucosidases of the tumor cells and lysosomal alpha-glucosidase of macrophages and leukocytes. These findings were corroborated by zymograms. T was detected in the same tumors as SI; its activity was lower, however. SI activity in colorectal tumors is a useful, but not general marker of these tumors.
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PMID:Sucrase-isomaltase and other brush border glycosidases in colorectal tumors. 886 57