Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of streptozotocin (SZ) on the development of small intestinal enzymes in postnatal rat pups was studied. SZ was injected ip on Day 10 and, if necessary, again on Day 12. On Days 15, 18, and 21, one pup from each group (including a vehicle-injected control (C) group) was decapitated under conditions which minimized stress. Plasma glucose, insulin (IRI), and corticosterone were measured, as were pancreatic IRI, liver glycogen, and liver membrane binding of IRI. Small intestinal segments were processed and analyzed for sucrase, lactase, maltase, and ileal acid beta-galactosidase activities. Our results indicate that plasma glucocorticoid levels remained virtually constant in both SZ and C groups, while the ontogenic profiles of sucrase and maltase in SZ rats were shifted toward an earlier appearance and a precocious maturation. Circulating levels of IRI were not reduced significantly by SZ despite the fact that pancreatic IRI was decreased 95%. Jejunal lactase, unlike data reported for diabetic rats, was not affected by SZ diabetes. Also, acid beta-galactosidase was unaltered in the SZ rat pups. It is concluded that possibly the elevated disaccharidases seen in diabetic postnatal rat pups are the direct effect of elevated blood glucose. If so, the SZ rat pup model may be a useful tool with which to study effects of glucose on intestinal enzymes in the absence of changes in plasma insulin.
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PMID:Effects of diabetes on development of small intestinal enzymes of infant rats. 312 20

Studies of intestinal enzyme development and regulation relevant to the human infant require an animal model with a rate of maturation similar to that of the human infant. Hanford miniature pigs were weaned at 3 days of age to a standard swine weaning formula. At 1, 2, 3, 4, 5, and 6 wk of age, duodenal jejunal, and ileal segments were analyzed for protein content and lactase, sucrase, maltase, glucoamylase, and acid beta-galactosidase activities. Protein content of the small intestine changed significantly with age only in the ileum (p less than 0.05). Lactase activity fell significantly with age in all segments of the small intestine (p less than 0.001); activity was highest in the jejunum. Sucrase and maltase activities were present in all segments of the small intestine at 1 wk of age. Sucrase increased significantly (2-fold, p less than 0.02) with age only in the ileum and maltase increased significantly with age in the jejunum (by 50%, p less than 0.05) and the ileum (3-fold, p less than 0.001). Activities were highest in the jejunum. Glucoamylase activity was present at 1 wk of age and showed a small but significant increase with age only in the duodenum (p less than 0.005). Acid beta-galactosidase activity demonstrated small but significant decreases with age in all small intestinal segments. Glucoamylase and acid beta-galactosidase activities were similar in all segments. In the 6-wk-old pigs, activities of all the enzymes tested were similar to those found in young human infants.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The miniature pig as an animal model for the study of intestinal enzyme development. 312 4

1. The intestinal disaccharidase activities of a suckling crabeater seal were investigated. 2. Lactase, maltase, isomaltase and cellobiase activities were readily detected but trehalase and sucrase activities were absent. 3. The intestinal homogenates were separated into a soluble (S2) fraction and a particulate brush border (P2) fraction. The lactase activities of the two fractions had different properties corresponding to those of an acid and a neutral beta-galactosidase respectively. Approximately two-thirds of the total lactase activity measured at pH 6.0 was due to the acid beta-galactosidase. 4. The isomaltase and cellobiase activities were found almost exclusively in the particulate fractions but about one third of the maltase activity was in the S2 fraction. This soluble maltase activity appeared to be due to an acid maltase.
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PMID:Intestinal lactase and other disaccharidase activities of a suckling crabeater seal (Lobodon carcinophagus). 313 70

Two genetic procedures were used to obtain amino acid replacements in the lacZ-encoded beta-galactosidase in Escherichia coli. Amino acid replacements could be obtained without regard to their effects on lactase activity by selecting spontaneous mutations that relieved the strong polarity of six nonsense mutations. When streaked on MacConkey-lactose indicator plates, approximately 75% of these mutants gave strong red lactose-fermenting colonies, and 25% gave white nonfermenting colonies. Mutants from 11 other nonsense codons were isolated directly using MacConkey-lactose indicator plates, on which positive color indication requires only 0.5% of the wildtype lactase activity. Among the total of 17 codons, 25 variant beta-galactosidases were identified using electrophoresis and thermal denaturation studies. The fitness effects of these variant beta-galactosidases were determined using competition experiments conducted with lactose as the sole nutrient limiting the growth rate in chemostat cultures. Three of the replacements were deleterious, one was selectively advantageous, and the selective effects of the remaining 21 were undetectable under conditions in which the smallest detectable selection coefficient was approximately 0.4%/generation.
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PMID:Fitness effects of amino acid replacements in the beta-galactosidase of Escherichia coli. 314 44

beta-Galactosidase from Saccharomyces lactis has been purified to serve as a model for the kinetic behavior of human lactase in adult lactase deficiency. Enzymes from both species are neutral and follow Michaelis-Menten kinetics. beta-Galactosidase of S. lactis is more readily available than the human lactase. An enzyme preparation from S. lactis (Maxilact 40,000), which is used commercially to hydrolyze lactose in milk, has been found to contain four isozymes of beta-galactosidase. Methods have been developed for the separation and purification of each of the four enzymes. The enzymes were found to differ in molecular mass, kinetic behavior, isoelectric point, response to pH, specific volume and sensitivity to metal ions. The four enzymes had apparent molecular masses of 630 kDa, 550 kDa, 41 kDa and 19 kDa. Their specificity constants (kcat/Km) were found to be 42.0, 355.2, 0.38 and 0.48 mM-1 s-1, respectively. The techniques of reiterated ultrafiltration used for the isolation of these isozymes may be applicable to other purification processes.
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PMID:Separation and characterization of four enzyme forms of beta-galactosidase from Saccharomyces lactis. 314 2

The relationship between primary lactase deficiency, the amount of lactose in the diet, and symptoms of intolerance continues to be debated. Primary adult lactase deficiency is common with a worldwide occurrence of near 70%. Lactase-deficient individuals malabsorb lactose but may or may not show intolerance symptoms. The development of symptoms appears to depend on the dose of lactose ingested, whether it is accompanied by a meal or other food, rate of gastric emptying, and small intestine transit time. Lactose loads of 15 g or greater produce symptoms in the majority of lactase-deficient persons. However, when lactose loads of up to 12 g are fed, symptoms can be minimal or absent. Tolerance to yogurt, acidophilus milk, and other microbe-containing dairy foods has been suggested and is thought to be due to either a low lactose content or in vivo autodigestion by microbial beta-galactosidase. Up to 20 g of lactose in yogurt is tolerated well by lactase-deficient persons. Associated with the consumption of yogurt is a three- to fourfold reduction in lactose malabsorption as compared with similar lactose consumption in milk. Improved lactose digestion appears due to autodigestion by microbial beta-galactosidase. This enzyme may be released from yogurt culture by gastric or bile acid digestion. Feeding yogurt that was pasteurized following fermentation, with only trace amounts of microbial beta-galactosidase activity, results in a threefold increase in lactose malabsorption as compared with feeding yogurt with a viable culture. However, pasteurized yogurt also is tolerated well by lactase-deficient persons, suggesting that tolerance of up to 20 g of lactose in yogurt may be independent of lactose malabsorption. The enhanced lactose absorption and tolerance observed with yogurt feeding are not apparent when unfermented acidophilus milk or cultured milk are fed.
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PMID:Milk intolerance and microbe-containing dairy foods. 355 56

1. Rats were fed on a control semi-synthetic diet containing insoluble cellulose (Solkafloc; 100 g/kg; control group) as the only source of dietary fibre, or on one of two test diets containing the same quantity of either guar gum or carboxymethylcellulose (CMC). Animals in the test groups showed similar growth rates and food intakes, which were significantly lower than those of the control group. The CMC group produced frequent poorly formed faeces throughout the 21 d feeding period. 2. The small intestines of animals in both test groups were significantly longer than those of the control group at the end of the study. The caeca were also enlarged and heavier, particularly in the CMC-fed group. 3. The rate of production of mucosal cells was increased in the small and large intestines of both test groups. The CMC-fed group exhibited a particularly high rate in the distal ileum, where the rate of cell divisions per crypt was over three times greater than at the same site in the control group. The increased proliferation was associated with a significant lengthening of the crypts and an approximately 25% increase in the basal width of the villi. 4. Mucosal alkaline phosphatase (EC 3.1.3.1) and lactase (EC 3.2.1.23) levels were lower than those of the control group at proximal and distal sites in the small intestines of both CMC- and guar-gum-fed groups. Altered spatial distributions of maltase (EC 3.2.1.20) and sucrase (EC 3.2.1.48) activities were also observed in these animals.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Gastrointestinal adaptation in response to soluble non-available polysaccharides in the rat. 367 72

The feasibility and efficacy of adding microbial beta-galactosidase enzymes directly to milk at the time of consumption was explored in adult lactose-malabsorbers. The hydrogen breath test, and on one occasion, the rise in blood glucose, were used as indices of the completeness of intraintestinal hydrolysis and absorption of milk lactose. When added to 360 ml of cow milk containing 18 g of lactose, empirical dosages of three beta-galactosidases--one from Kluyveromyces (yeast) and two from Aspergillus (fungal)--had some effectiveness in reducing postprandial H2 excretion, although no in vivo treatment at the dosages chosen was as effective as pre-incubation of the milk in vitro. The yeast enzyme also reduced symptom frequency as compared to intact milk and enhanced postprandial rises in blood glucose. The replacement therapy with exogenous, food-grade beta-galactosidases may provide a useful intervention to reduce lactose malabsorption and milk intolerance in individuals with primary lactase deficiency.
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PMID:Dietary manipulation of postprandial colonic lactose fermentation: II. Addition of exogenous, microbial beta-galactosidases at mealtime. 391 30

The feasibility of enzyme replacement therapy with exogenous, food-grade, microbial enzymes at mealtime to effect intragastrointestinal hydrolysis of the lactose from 360 ml of cow's milk consumed with a solid food meal (breakfast cereals) was investigated in adult Guatemalan lactose-malabsorbers using a hydrogen breath-analysis procedure to quantify the completeness of postprandial carbohydrate absorption. Adding 2 g of a commercial preparation of beta-galactosidase from Kluyveromyces lactis at mealtime to milk taken with a refined cereal (cornflakes) and an unrefined cereal (bran) reduced the production of excess breath H2 attributable to lactose maldigestion to a level not significantly different from that achieved with lactose-prehydrolyzed milk. Sucrase, as expected, had no effect on H2 production. A beta-galactosidase from Aspergillus niger was less effective that the K. lactis enzyme for in vivo hydrolysis. Thus, exogenous betagalactosidases can eliminate lactose malabsorption in lactase-deficient individuals even in the presence of solid foods, allowing lactose intolerant persons to consume milk and dairy products without gastrointestinal discomfort.
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PMID:Effective in vivo hydrolysis of milk lactose by beta-galactosidases in the presence of solid foods. 391 31

We have examined the nature of the decline of lactase (EC 3.2.1.23) activity in the maturing rat intestine. It was established in an initial study that the activity decline reflected a proportional reduction in the concentration of the enzyme protein. Accumulation patterns of label into lactase, total intestinal proteins and sucrase (EC 3.2.1.48)-isomaltase (EC 3.2.1.10) were compared, 4 h following administration of a tracer dose of [3H]leucine to weanling rats exhibiting a wide range of lactase decline. Accumulation of increasing amounts of label in total intestinal proteins and sucrase-isomaltase pools was found to accompany the lactase decline, in contrast to accumulation of a constant amount of label in the declining lactase pools. The pattern of increased label accumulation in total intestinal proteins was shown in a corollary study to reflect a corresponding acceleration of total protein synthesis. On this basis, the finding of a constant amount of label in the declining lactase pools suggested a constant synthesis of lactase. We proposed earlier that associated reductions in enterocyte life-span (leading to correspondingly less lactase accumulation) rather than suppressed synthesis may provide the primary causal basis of lactase decline in the postweaned mammal.
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PMID:The nature of maturational decline of intestinal lactase activity. 392 28


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