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)

The initial step of disaccharide dissimilation by Actinomyces viscosus serotype 2 strain M-100 was studied. Sucrase activity was found in the 3,000 X g particulate fraction and the 37,000 X g soluble fraction of the cells, whereas lactase activity was found almost exclusively in the 37,000 X g soluble fraction. Neither sucrase nor lactase activity was appreciable in the culture liquor. Sucrose phosphorylase, alpha-glucosidase, and polysaccharide synthesis activities were not observed in the soluble cell fraction. The sucrase was identified as invertase (EC 3.2.1.26; beta-D-fructofuranoside fructohydrolase). The lactase was identified as beta-galactosidase (EC 3.2.1.23; beta-D-galactoside galactohydrolase). The enzymes in the 37,000 X g soluble fraction were separable by diethylamino-ethyl-cellulose chromatography, giving one beta-galactosidase peak and one major and one minor invertase peak. Acrylamide gel electrophoresis showed different electrophoretic mobilities of the enzymes. The molecular weight of the beta-galactosidase is about 4.2 X 10(5) and that of invertase is about 8.6 X 10(4). The beta-galactosidase has a Km for lactose of about 6 mM and a pH optimum between pH 6.0 and 6.5. The major invertase component has a Km for sucrose of about 71 mM and a pH optimum between pH 5.8 and 6.3.
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PMID:Identification, separation, and preliminary characterization of invertase and beta-galactosidase in Actinomyces viscosus. 1 74

1. Sugar-containing diets chosen not to affect intestinal structure or enterocyte turnover have been fed to mice previously maintained on a low carbohydrate diet in order to determine their ability to induce disaccharidase enzymes in the small intestine. 2. Glucose-, fructose- and 3-O-methyl-glucose-containing diets increased sucrase and maltase but not lactase activities in mouse jejunal homogenates. These effects were either absent or negligible in more distal regions of the small intestine. 3. Placing mice on glucose-, fructose- or 3-O-methyl-glucose-containing diets was further shown, by quantitative cytochemistry, to cause a 1.6-, 2.6- and 3.2-fold increase in the initial rate at which alpha-glucosidase activity (sucrase + maltase) appeared in the brush-border membrane of developing enterocytes. 4. The time during which alpha-glucosidase activity increased in enterocyte brush-border membranes fell from 30 h for low carbohydrate fed mice to 21, 19 and 17 h in mice fed glucose, fructose and 3-O-methyl-glucose respectively. Change of diet had no effect on the kinetics of lactase expression by developing enterocytes. 5. Maximal alpha-glucosidase activity detected in enterocyte brush-border membranes is equal to RT, where R is the initial rate of enzyme appearance and T is the time during which this rate operates. The ability of sugars to increase R selectively, but only at the expense of T, defines unexpected limits to the capacity of enterocytes to adapt to changes in luminal nutrition. 6. The above results are discussed in relation to other aspects of enterocyte differentiation recently subjected to quantitative analysis. The need to standardize other aspects of intestinal physiology and redefine the energy content of diets containing non-metabolizable substrates in this type of work is also emphasized.
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PMID:Sugar-dependent selective induction of mouse jejunal disaccharidase activities. 251 26

Twelve female Wistar rats, weaned at 21 days, were allocated in two groups: Lactose Group composed by six rats receiving a normal laboratory diet added with 25 g of lactose for each 100 g of final mixture, and the Saccharose Group that was fed with the same diet but with the lactose being replaced by saccharose in the same proportion; both groups were studied for 28 days. The rats were weighed at the beginning of the experiment and on the 7th, 14th, 21st and 28th days; the relative ingestion of water and diet was evaluated for each animal on the same days except for the first. During the observation period weight gain was significantly lower on the Lactose Group compared to the Saccharose Group, although this difference became less evident towards the end of the experiment. In the Lactose Group the diet ingestion was higher on the 21st and 28th days opposed to the water ingestion which was higher on the 7th and 14th days. The results here presented suggest that, in spite of the ontogenic fall of intestinal lactase in rats, these animals can, even after weaning, accommodate to high doses of dietary lactose, by using adaptative pathways which deserve further investigation.
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PMID:[Adaptation of rats, after weaning, to a diet with a high concentration of lactose. I. Evaluation of water and diet ingestion]. 314 67

Diarrhoea was a common problem in the kwashiorkor seen in Kampala, contributing to the mortality and delay in recovery. Enteric infection was found in only a few children (8%), but when present it caused particularly severe diarrhoea and was frequently complicated by septicaemia.Sugar intolerance often occurred to lactose and other sugars, both monosaccharide and disaccharide. The children were most commonly intolerant of lactose, and some of these may have had a hereditary lactase deficiency.Antibiotics are rarely indicated for the treatment of diarrhoea in kwashiorkor in Kampala. If reducing substances are found in the stool of a child on a milk diet, a diet based on sucrose is substituted, and if intolerance persists a fructose diet is given. A few children are intolerant of all sugars, including fructose, and for these the prognosis is grave.
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PMID:Diarrhoea in kwashiorkor. 488 39

The specific effect of dietary sugars on jejunal disaccharidase activity in seven normal nonfasted male volunteers was studied. The sugars tested were sucrose, maltose, lactose, glucose, fructose, and galactose. Comparisons were made of the effects of each sugar in an isocaloric liquid diet. In all subjects, sucrose feeding, as compared to glucose feeding, significantly increased jejunal sucrase (S) and maltase (M) activities, but not lactase (L) activity. The S/L and M/L ratios increased to a significant degree. Fructose feeding, in two subjects, gave results similar to sucrose when comparing fructose and glucose diets. One subject was fed lactose, galactose, and maltose. These sugars, compared to glucose, did not increase disaccharidase activity. Fructose appears to be the active principle in the sucrose molecule. These results demonstrate that specific dietary sugars can alter enzyme activity in the small intestine of man in a specific fashion. Sucrose and fructose are able to regulate sucrase and maltase activity. Dietary alteration of intestinal enzymes may represent a suitable system for studying the regulation of enzyme activity in man.
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PMID:Control of jejunal sucrase and maltase activity by dietary sucrose or fructose in man. A model for the study of enzyme regulation in man. 567 20

The administration of a carbohydrate-containing diet for 24 hours to rats previously fasted for 3 days led to a twofold increase in total intestinal sucrase and sucrase specific activity. The specific activity of maltase was similarly increased, but lactase activity was unaffected. The sucrose-containing diet led to a greater increase in sucrase than maltase activity, whereas the converse was true of the maltose-containing diet. A carbohydrate-free isocaloric diet led to a slight increase in the total intestinal sucrase, but sucrase specific activity was unchanged. Assay of sucrase activity of mixed homogenates from casein-fed and sucrose-fed rats or fasted and sucrose-fed animals yielded activities that were additive. The Michaelis constant (Km) of the enzyme hydrolyzing sucrose was similar in the fasted, casein-fed, and sucrose-fed rats. The maximal velocity (Vmax) was twice greater in sucrose-fed as compared to casein-fed or fasted rats, suggesting an increased quantity of enzyme subsequent to sucrose feeding. Adrenalectomized rats maintained on 1.0% salt intake had sucrase and maltase levels comparable to those of controls. Steroid administration did not significantly increase their activities. The response to sucrose feeding was similar in both control and adrenalectomized rats, indicative of the absence of steroidal control on sucrase and maltase activity in the adult animal. Studies using intestinal ring preparations indicated that sucrose hydrolysis by the intact cells proceeded more rapidly when animals were fed sucrose. Additional corroboration of the physiologic significance of the increased enzyme levels in homogenates was afforded by intestinal perfusion studies. Sucrose hydrolysis increased twofold and fructose absorption fourfold in animals fed sucrose when compared to either fasted or casein-fed rats.
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PMID:Effect of diet upon intestinal disaccharidases and disaccharide absorption. 601 58

An oral sucrose tolerance test was performed in a group of 103 children, aged between 3 months and 15 years because of episodic diarrhea and/or abdominal pains. Sucrose malabsorption defined as an abnormal increase in expired hydrogen, was found in only 3 children who suffered from congenital sucrase-isomaltase deficiency. This 1% incidence of sucrose malabsorption was lower than the incidence of lactose malabsorption found in this group (33%). Mean rise in blood glucose during the sucrose test was higher (3.4 +/- 1.4 vs. 2.4 +/- 1.2 mmol/l, p less than 0.0001) and the occurrence of false flat blood glucose curves was lower (3% vs. 12.8%, p less than 0.05) than during the lactose test. These findings are consistent with the higher sucrase activity in the small bowel mucosa compared to lactase. In contrast to the lactose tolerance test, sucrose tolerance test should not be used as a screening procedure for secondary disaccharidase deficiency in children.
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PMID:Diagnostic value of sucrose tolerance test in children evaluated by breath hydrogen measurement. 736 16

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

Intestinal glycohydrolases are enzymes involved in assimilating carbohydrate for nutrition. The avian forms of these enzymes, in particular the maltase-glucoamylase complex (MG), are not well characterised. This study encompassed characterisation of these enzymes from ostrich intestines, and the first kinetic analysis of an avian MG. Proteolytically solubilised MG from ileal brush border membrane vesicles was purified by Sephadex G-200 gel filtration and Tris-affinity-chromatography, while jejunal sucrase-isomaltase (SI) and MG were purified by Toyopearl-Q650 and phenyl-Sepharose chromatography. Amino acid sequences and compositions of enzyme subunits, resulting from SDS-PAGE, were determined. Kinetics of hydrolysis of linear oligosaccharides was studied. Ostrich MG and SI showed the highest activity in the jejunum, followed by the ileum and duodenum. No lactase or trehalase activity could be detected. The jejunal MG and SI, resulting from brush-border membrane vesicles, could not be separated during purification. However, a minor form of ileal MG was purified using Sephadex G-200 chromatography. Ileal MG contained three subunits of M(r) 145,000, 125,000 and 115,000. Although the N-terminal amino acid sequences bear no homology to SI, the M(r) 115,000 subunit shows homology to porcine MG in both sequence and amino acid composition. The pH optimum of maltose-, starch- and isomaltose-hydrolysing activity was 6.5 and that of sucrose-hydrolysing activity 5.5. The glycohydrolases were most active at 58 degrees C, but were quickly denatured above 60 degrees C. Sucrose- and starch-hydrolysing activities were more thermostable than maltose- and isomaltose-hydrolysing activities. Kinetic parameters (K(m), kcat and kcat/K(m)) for the hydrolysis of maltooligosaccharides, starch and glycogen are reported for ileal MG. Maltotriose and maltotetraose displayed partial inhibition of ileal MG. The study revealed large similarities between ostrich SI and MG in charge, size, shape and hydrophobicity, based on their inseparability by several methods. Measurement of the specificity constants for maltooligosaccharide hydrolysis by ileal MG revealed less efficient hydrolysis of longer substrates as compared to maltose and maltotriose.
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PMID:Ostrich intestinal glycohydrolases: distribution, purification and partial characterisation. 961 76

In vitro and in situ findings suggest an impairment of digestive and absorptive functions in the small intestine by enteral cadmium salts. In the rat, diets with up to 1 mmol Cd/kg are well tolerated, however, so that the impairment might not be this drastic or compensated by adaptive changes. To elucidate whether small intestinal functions are altered, we studied the effect of dietary cadmium on the longitudinal pattern of mucosal enzymes and the in vitro uptake of methyl alpha-D-glucoside in the small intestine of female rats. Three groups of rats were employed, a control group and two groups receiving dietary CdCl2 either at 0.3 or 1.0 mmol Cd/kg of diet. Rats were killed after 1 week of feeding. The entire small intestine was removed, rinsed with ice-cold saline and divided into 12 segments of equal length. Mucosal scrapings from each segment were used to measure mucosal cadmium levels, sucrase, lactase, alkaline phosphatase, glycylleucine-hydrolase, and diamine oxidase activities. Sugar uptake was determined in vitro in all segments using everted rings tissue accumulation method. Although cadmium levels in the mucosa were high (>100 ng Cd/mg protein or >100 micromol Cd/kg WW) most enzyme activities were only slightly changed. When significant decreases in activity were detected, they were only observed in the proximal small intestine. Sugar uptake was also impaired only in proximal segments, the maximal transport capacity was reduced by approximately 20%. These findings suggest that cadmium even at dietary levels of 1 mmol/kg do not lead to a drastic impairment of digestive and absorptive functions in the small intestine and that in the rat presently observed, mostly proximal impairments are easily compensated by unaltered distal functions. Certainly, absorption of micronutrients, for which an impaired proximal function cannot be compensated, e.g. iron, might be critical in this respect.
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PMID:Longitudinal pattern of enzymatic and absorptive functions in the small intestine of rats after short-term exposure to dietary cadmium chloride. 1004 3


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