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)

The regulatory mechanism of decline in catalytic activity for intestinal lactase (lactase-phlorizin hydrolase, beta-galactosidase) as mammals mature has not been defined. Solubilized intestinal brush-border membranes from adult male rats (greater than 4 months of age, 200-400 g) were examined by high performance liquid Zorbax GF-450 chromatography, subjected to denaturing acrylamide electrophoresis, blotted to nitrocellulose, and identified by specific polyvalent anti-lactase. Three major species were present within the 235-kDa active lactase peak (225, 130, and 100 kDa). The 100-kDa moiety was also prominent in the approximately 300-kDa region of the GF-450 effluent, suggesting it is a catalytically inactive oligomer. In vivo synthesis and assembly of lactase by intraintestinal pulse [( 35S]methionine, 5 min) and chase (15-120 min) revealed rapid (15 min of chase; maximum, 60 min) intracellular synthesis in the endoplasmic reticulum-Golgi fraction of multiple species (64, 100, 130, 175, and 225 kDa). The 64-kDa species disappeared from the intracellular membrane compartment and was not transferred to the brush-border surface. The 175-kDa moiety appeared to be processed to the 225-kDa unit prior to relocation to the surface membrane. By 120 min, the 100-kDa species became the predominant (approximately 60%) radiolabeled unit in both endoplasmic reticulum-Golgi and brush border. In the adult rat, lactase is assembled in multiple molecular forms that are differentially processed: (a) intracellular degradation (64-kDa unit) or (b) transfer to the brush-border surface as catalytically active (225 and 130 kDa) or inactive (100 kDa) species. Although substantial synthesis of lactase proteins prevails, major changes in processing appear to serve as an important regulatory mechanism producing the maturational decline of catalytic activity. The accompanying article (Castillo, R. O., Reisenauer, A. M., Kwong, L. K., Tsuboi, K. K., Quan, R., and Gray, G. M. (1990) J. Biol. Chem. 265, 15889-15893) extends our studies to synthesis and assembly during the neonatal period of maturation.
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PMID:Intestinal lactase. Shift in intracellular processing to altered, inactive species in the adult rat. 211 32

During studies on the Golgi apparatus immunolocalization of beta-galactoside alpha 2,6-sialyltransferase in intestinal cells, immunostaining of a number of post-Golgi apparatus structures including mucus droplets and plasma membrane were observed. In order to determine if this labeling was in fact due to sialyltransferase and not carbohydrate-specific antibodies in the polyclonal antiserum preparation, fusion protein to sialyltransferase was used to epitope purify polypeptide-specific antibodies. The affinity purification was performed on a column containing a beta-galactosidase-sialyltransferase fusion protein expressed in Escherichia coli. Using such antibodies we present evidence that in intestinal cells sialyltransferase is not only present in the Golgi apparatus cisternal stack but also its transtubular network and various post-Golgi apparatus structures. In absorptive enterocytes, post-Golgi apparatus vesicles, the brush border and basolateral plasma membrane, multivesicular bodies, and lysosome-like structures were labeled. In goblet cells the limiting membrane and lumen of forming and mature mucus droplets as well as the plasma membrane exhibited label for sialyltransferase. The results provide evidence for "ecto-sialyltransferase" in the plasma membranes of these cells, and suggest that most of the sialyltransferase is released from the Golgi membranes and becomes secreted with the goblet cell mucus. In addition, the polypeptide epitope-purified antibody was also used to examine regional expression of sialyltransferase in the rat intestinal epithelium. Immunolabel was restricted to the large intestine and not found in duodenum, jejunum, and ileum. Direct measurement of the enzyme activity was found to correlate with the immunoelectron microscopic data. This observation suggests that there is regional specific expression of the beta-galactoside alpha 2,6-sialyltransferase.
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PMID:Post-Golgi apparatus localization and regional expression of rat intestinal sialyltransferase detected by immunoelectron microscopy with polypeptide epitope-purified antibody. 245 61

We report the primary structures of human and rabbit brush border membrane beta-glycosidase complexes (pre-pro-lactase-phlorizin hydrolase, or pre-pro-LPH, EC 3.2.1.23-62), as deduced from cDNA sequences. The human and rabbit primary translation products contain 1927 and 1926 amino acids respectively. Based on the data, as well as on peptide sequences and further biochemical data, we conclude that the proteins comprise five domains: (i) a cleaved signal sequence of 19 amino acids; (ii) a large 'pro' portion of 847 amino acids (rabbit), none of which appears in mature, membrane-bound LPH; (iii) the mature LPH, which contains both the lactase and phlorizin hydrolase activities in a single polypeptide chain; (iv) a membrane-spanning hydrophobic segment near the carboxy terminus, which serves as membrane anchor; and (v) a short hydrophilic segment at the carboxy terminus, which must be cytosolic (i.e. the protein has an Nout-Cin orientation). The genes have a 4-fold internal homology, suggesting that they evolved by two cycles of partial gene duplication. This repetition also implies that parts of the 'pro' portion are very similar to parts of mature LPH, and hence that the 'pro' portion may be a water-soluble beta-glycosidase with another cellular location than LPH. Our results have implications for the decline of LPH after weaning and for human adult-type alactasia, and for the evolutionary history of LPH.
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PMID:Complete primary structure of human and rabbit lactase-phlorizin hydrolase: implications for biosynthesis, membrane anchoring and evolution of the enzyme. 246 Mar 43

Small-intestinal disaccharidase activities of eight suckling T. vulpecula, aged from 34 to 150 days, and of two adult animals were investigated. Intestinal maltase, isomaltase and sucrase activities increased with age, whereas lactase activities decreased. Trehalase activities were relatively high in all animals and showed no obvious age-related changes. Three separate beta-galactosidase activities, one neutral and two acid, acted on lactose. The neutral beta-galactosidase activity appeared to be due to a brush border enzyme similar to that of eutherian mammals, whereas the acid beta-galactosidases were soluble and probably of lysosomal origin. One of these, acid beta-galactosidase-1, had similar properties to the sole intestinal beta-galactosidase of macropodid marsupials, whereas the other, acid beta-galactosidase-2, has not previously been described. Galactosyl oligosaccharides isolated from macropodid milk were readily hydrolysed by both acid beta-galactosidases but not by the neutral beta-galactosidase. The total intestinal lactase activity in animals aged up to 125 days was due mainly to acid beta-galactosidase-1, whereas in older animals it was due mostly to the neutral beta-galactosidase; this suggests that late in lactation the young T. vulpecula change from a macropodid mode of digestion of galactosyl oligosaccharides to a eutherian mechanism for the digestion of lactose. These findings may have implications for the hand-rearing of orphaned T. vulpecula.
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PMID:Intestinal lactase (beta-galactosidase) and other disaccharidase activities of suckling and adult common brushtail possums, Trichosurus vulpecula (Marsupialia:Phalangeridae). 251 66

The inhibitory action and mechanism of inhibition of two types of alpha-glucosidase inhibitors, acarbose (Bay-g-5421) and 1-deoxynojirimycin derivatives (Bay-m-1099 and Bay-o-1248), on small intestinal carbohydrases (sucrase, isomaltase, glucoamylase, trehalase and lactase) and pancreatic alpha-amylase were compared in vitro using small intestinal brush border membranes and pancreatic homogenates from adult Sprague-Dawley rats. Acarbose at a low (4 microM) concentration strongly inhibited the activities of glucoamylase, alpha-amylase and sucrase (98, 68, and 63%, respectively). At a high (200 microM) concentration, isomaltase activity was also inhibited (28%); effects on trehalase and lactase activities were negligible. Both the 1-deoxynojirimycin derivatives were even more potent inhibitors of sucrase (Ki = 8.6 x 10(-8) M for Bay-m-1099;Ki = 5.0 X 10(-8) M for Bay-o-1248) than acarbose (Ki = 9.9 x 10(-7) M). Whereas glucoamylase activity was strongly inhibited by the 1-deoxynojirimycin derivatives, alpha-amylase activity was not. In contrast to acarbose, the 1-deoxynojirimycin derivatives at high concentrations (20-200 microM) inhibited considerably trehalase and lactase (a beta-galactosidase) activities. The inhibition of lactase activity was stronger by Bay-m-1099 (Ki = 4.9 X 10(-6) M) than by Bay-o-1248 (Ki = 6.7 X 10(-5) M). Where inhibition was seen, kinetic analysis showed fully competitive inhibition of sucrase, isomaltase, trehalase, glucoamylase and lactase by all three inhibitors.
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PMID:Inhibitory mechanism of acarbose and 1-deoxynojirimycin derivatives on carbohydrases in rat small intestine. 296 44

To evaluate the response of the small intestinal mucosa to Saccharomyces boulardii (S.b.), a yeast widely used in some countries as an adjuvant drug with oral antimicrobial therapy, seven healthy adult volunteers were treated with high doses of lyophilized S.b. (250 mg four times per day) for 2 wk. A peroral jejunal suction biopsy was performed on days 0 and 15 of the study. Compared to the initial biopsy, histological examination of the posttrial biopsy revealed no morphological alteration nor change in villus height or crypt depth. After treatment, the specific activity (per U protein) of sucrase, lactase, and maltase was, respectively, increased by 82% (p less than 0.05) 77% (p less than 0.05), and 75% (p less than 0.05) over the basal activity of the enzymes measured on day 0, whereas mucosal protein content remained unchanged. Similar findings were found in the jejunum of adult rats treated for 5 days with either viable or killed S.b. cells. The changes in total enzyme activity (per jejunal segment) paralleled the changes in specific enzyme activity. In vitro assays on freshly prepared suspensions of S.b. (6.0 X 10(8) viable cells/ml) evidenced a high activity for sucrase (mean +/- SE: 8 364 +/- 1280 U X g X protein-1) but no maltase, neutral lactase, acid beta-galactosidase, or aminopeptidase activity. To determine whether treatment with S.b. could influence the incorporation rate of neutral lactase into the brush border membrane, 14-day-old sucklings treated either with saline or with S.b. were given intraperitoneally a dose of 20 microCi D-[1(14)C] glucosamine 3 hours before sacrifice.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Response of human and rat small intestinal mucosa to oral administration of Saccharomyces boulardii. 308 Jul 30

Comparative histochemical studies of glycosidase activity were carried out in Clonorchis sinensis, Eurytrema pancreaticum, Fasciola hepatica, Dipylidium caninum, Hymenolepis nana, Ascaris suum, Toxocara canis, Ancylostoma caninum, Trichuris vulpis and Dirofilaria immitis. The enzymes examined were: N-acetyl-beta-glucosaminidase (EC 3.2.1.30), beta-glucuronidase (EC 3.2.1.31) and beta-galactosidase (EC 3.2.1.23). There were variations in enzyme distribution and intensity among the species and also between trematodes and nematodes; no marked positive reaction for these enzymes occurred in cestodes. In some trematodes, the caeca, especially in the brush border, and the tegument, subtegumental cells and testes, were reactive to the enzymes. In nematodes, although there was variation in reactions among species, N-acetyl-beta-glucosaminidase and beta-galactosidase were localized in the hypodermis and lateral cords excluding the excretory canal, and coelomocytes, intestinal epithelium and the walls of the reproductive systems.
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PMID:Comparative histochemical studies of glycosidase activity in some helminths. 308 22

The activities of the enterocyte brush border enzymes lactase (beta-D galactoside galactohydrolase, EC 3.2.1.23) and sucrase (sucrose alpha-D glucohydrolase, EC 3.2.1.48) were measured at set percentage lengths along the small intestines of 112 piglets killed between 21 and 32 days of age. The influences on these activities of consumption of creep feed and of weaning were recorded. Weaning at three weeks old resulted in large, rapid reductions in lactase activity at most sites along the small intestine; sucrase activity declined temporarily and then recovered. Minimum values were recorded about four to five days after weaning. Similar changes were observed whether or not creep feed was consumed before weaning. Continued consumption of creep feed by unweaned pigs over the 21 to 32 day period also produced small but significant reductions in lactase activities. The large loss of digestive enzyme activities at brush borders in weaned animals coincided with a reduced ability to absorb xylose and to checks in growth rate in otherwise healthy piglets.
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PMID:Influence of creep feeding and weaning on brush border enzyme activities in the piglet small intestine. 308 80

Hydrocortisone administration to infant rats enhanced cellobiase and maltase activities and induced precocious expression of sucrase and trehalase activities along the length of the small intestine. These activity changes reflected proportional concentration increases in the enzymes lactase (EC 3.2.1.23), maltase/glucoamylase (EC 3.2.1.20) and sucrase-isomaltase (EC 3.2.1.48/10). Administration of an equivalent tracer dose of [3H]leucine (by body weight) to control and hydrocortisone-treated infant rats resulted in greater accumulation of label in the carbohydrase pools of the treated rats, suggesting their increased de novo synthesis. The increased concentrations of lactase and maltase/glucoamylase induced by exogenous hydrocortisone were matched by the presence of corresponding greater amounts of label in their brush border pools. Accumulation of label in each of the lactase, maltase/glucoamylase and sucrase-isomaltase pools was generally similar in the hydrocortisone-treated rats, suggesting equivalent stimulation of their synthesis as a group by the humoral agent. The turnover rates of the carbohydrases as a group were found to be similar and did not appear to differ in control and hydrocortisone-treated rats. Total protein synthesis rates were slightly greater in the intestine of the hydrocortisone-treated group of rats.
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PMID:Effects of hydrocortisone on carbohydrase concentrations, de novo synthesis and turnover patterns in immature rat intestine. 308 73

The biosynthesis and maturation of the human intestinal lactase-phlorizin hydrolase (LPH; EC 3.2.1.23-3.2.1.62) has been studied in cultured intestinal biopsies and mucosal explants. Short time pulse labelling revealed on high mannose intermediate of Mr 215,000 which was converted upon endo-beta-N-acetylglucosaminidase H (endo-H) digestion to a polypeptide of Mr 200,000. The brush border form of LPH was revealed after longer pulse periods and has Mr 160,000. It possesses mainly complex oligosaccharide chains and, owing to its partial endo-H sensitivity, at least one chain of the high mannose type. Leupeptin partially inhibited the appearance of the Mr-160,000 polypeptide. Monensin treatment of biopsies resulted in the modification of the Mr-160,000 species to the Mr-140,000 molecule, which was endo-H sensitive. Pulse-chase analysis indicated a slow post-translational processing of the high mannose precursor (Mr 215,000) to yield the mature brush-border form (Mr 160,000) of LPH. Our results further indicate that LPH is synthesized as a single polypeptide precursor which is intracellularly cleaved to yield the mature brush border of LPH. The data presented suggest that this cleavage occurs during the translocation of the molecule across the Golgi complex.
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PMID:Biosynthesis and maturation of lactase-phlorizin hydrolase in the human small intestinal epithelial cells. 310 75


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