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

The ability of the horse to digest and absorb soluble carbohydrates was assessed using a series of oral disaccharide tolerance tests followed in the same animals by tolerance tests with the constituent monosaccharides. In horses older than three years, lactose did not produce an increase in the plasma glucose levels but induced the passing of soft faeces, indicating that adult horses are lactose intolerant. Horses of all ages could absorb the glucose: galactose mixture without any change in the faeces. The tolerance is due to a failure to hydrolyse lactose and does not involve the monosaccharide transport systems. These findings correspond to the known development pattern of brush border lactase activity in the equine small intestine. Both sucrose and maltose were rapidly hydrolysed, the resulting tolerance curves closely approximating to those for the constituent monosaccharides. Galactose was absorbed at a similar rate to glucose, although a dose of 1g/kg was necessary to produce galactosaemia. An oral lactose tolerance test (1 g/kg as a 20 per cent solution) could be of clinical value to determine small intestinal mucosal damage in diarrhoeic foals when the continued ingestion of lactose might be detrimental.
 ...
PMID:Carbohydrate digestion and absorption studies in the horse. 111 66

The present work investigates the ability of galactose to affect enterocyte differentiation during normal development in vivo. Energy intake has also been varied to take account of the fact that galactose is poorly metabolized in mice. Brush-border lactase, alpha-glucosidase, dipeptidylpeptidase-IV, aminopeptidase N, alkaline phosphatase and microvillus length were measured as markers of enterocyte differentiation in mice fed diets containing galactose (G diet), corn oil (E diet) or galactose + corn oil (G + E diet). Maintaining mice on a G instead of E diet reduced brush-border lactase activity and enterocyte migration rates; alpha-glucosidase, dipeptidylpeptidase-IV, aminopeptidase N and microvillus length expression increased and alkaline phosphatase activity remained unchanged. Feeding the G + E diet restored enterocyte migration rates, lactase, aminopeptidase N and dipeptidylpeptidase-IV activities to values found in mice fed the E diet. Galactose stimulation of alpha-glucosidase and microvillus length expression was, however, fully maintained in mice fed the G + E diet. Present results show that enterocyte differentiation is affected independently by varying dietary galactose and energy levels; that galactose effects always increase and energy effects usually decrease expression of enterocyte components and that energy stimulation of lactase activity is exceptional.
 ...
PMID:Galactose effects on enterocyte differentiation in the mouse jejunum. 190 92

Present work uses a combination of quantitative cytochemistry and measurements of cell migration rates to describe galactose effects on lactase expression by mouse enterocytes. Mice fed galactose were found to eat less, weigh less and drink more than mice maintained on a low-carbohydrate isocalorific diet. The enterocyte migration rate in these mice was also only one third of that determined in low-carbohydrate-fed animals. The rate at which lactase activity increased in the brush border membrane of migrating enterocytes was 3-times greater in low-carbohydrate- compared with galactose-fed mice. The time during which this increase persisted was, however, 3-times less in low-carbohydrate-fed animals. The maximum rate of sucrase-maltase appearance, measured as control in these experiments, remained unaffected by galactose feeding. Galactose effects on lactase expression might in part result from mice being unable to metabolise this substrate. Previously it has been stated that galactose increases lactase biosynthesis in rat intestine (Koldovsky, O., Bustamonte, S. and Yamada (1981) In Mechanisms of intestinal adaptation (Robinson, J.W.L., Dowling, R.H. and Ricken, E.O., eds.), pp. 153-156, MTP Press, Lancaster). This result is discussed in relation to the opposite finding reported in the present work for mouse jejunal enterocytes. The need to relate enzyme appearance to age and developmental state of enterocytes in this type of study is also emphasized.
 ...
PMID:Galactose inhibits lactase expression by mouse jejunal enterocytes. 210 3

The effect of supplementation of the diet with galactose on the age-related decline of intestinal lactase activity was investigated in 108 growing rats. Starting from 14 days of age, the rats were divided into two groups and fed with chow, and with fluid either as tap water or 5% galactose solution. At 14 days the specific lactase activity was 112.8 +/- 3.2 mumol min-1 (g protein)-1, which decreased to less than 10% of this value at maturity. Galactose supplementation did not prevent the decline. The increase of maltase, sucrase and trehalase was also unaffected. The result suggests that galactose plays no significant role in the regulation of disaccharidase activities in the rat.
 ...
PMID:The effect on intestinal disaccharidase activity of feeding galactose to growing rats. 224 21

A magnetic immobilized lactase has been prepared using magnetite as the magnetic material. Magnetite was functionalized by treatment with polyethyleneimine and crosslinked with glutaraldehyde. Lactase was then covalently coupled to the activated magnetic matrix via the aldehyde groups. The conditions for optimal immobilization of enzyme are described. Eighty percent of the lactase activity was lost on immobilization and is thought to be owing to the orientation of enzyme binding to the matrix. The amount of protein coupled was 80% of that applied. The maximum lactase activity retained on the matrix following immobilization was 360 U/g matrix. The immobilized lactase showed optimal activity at pH 4.5 and 65 degrees C. The immobilized lactase was more heat stable than the free enzyme, and retained 83% of its original activity after 14 d at 55 degrees C. Galactose competitively inhibited the immobilized lactase preparation (Ki 20 m/M). The presence of high initial concentrations of galactose (10% w/v) did not prevent total hydrolysis of lactose. Glucose and calcium ions were activators of the immobilized enzyme. The immobilized enzyme hydrolyzed high concentrations of lactose (up to 25% w/v) to completion within 4-6 h in a stirred batch reactor at 55 degrees C. There was no evidence of substrate inhibition at high substrate concentrations. The efficiency of hydrolysis of lactose by the immobilized lactase was better than that of the free enzyme. The magnetic immobilized lactase was demonstrated to be suitable for use in the enzymatic hydrolysis of both pure, and cheese whey permeate, lactose.
 ...
PMID:Immobilization of a lactase onto a magnetic support by covalent attachment to polyethyleneimine-glutaraldehyde-activated magnetite. 251 53

Nutritional balances are made with groups of 12 rats Wistar receiving well-balanced diets with 40 p. 100 of sucrose (T), or 40 p. 100 of lactose (L and P), or hydrolyzed lactose (LH and PH). Whey (L) and ultrafiltration permeate (P) are used in crude state or after enzymic industrial lactase hydrolysis (LH and PH). The animals consume diets during eight months. Faeces contain neither lactose nor galactose, but glucose in small quantities. In all urines occurs about 0,5 mg/day of glucose. The lactose diets (L and P) provoke a week lactosury (0,36 p. 100 of ingestion). Galactose and galactitol are abundant in urines: with lactose diets (L and P), the urinary excretion is equal to 4 p. 100 of ingested galactose. In urines of hydrolyzed lactose diets (LH and PH) the excretion reaches 26 p. 100 of ingestion. In this case the excretion is remarkably invariable from third day of eighth month: the urinary galactose corresponds to 23 p. 100 and galactitol to 3 p. 100 of consumed galactose. The urines of lactose diets (L and P) and hydrolyzed lactose diets (LH and PH) contain 100 and 300 mg/day of non sugar reducing substances respectively, i.e. 40 p. 100 of total urinary reducing power. The apparent retention of lactose (L and P) is 95,5 p. 100 and that of the hydrolyzed lactose (LH and PH) is 86 p. 100 after 8 months of experiment but it is estimated that digestive flora consumes 40 p. 100 of dietary lactose (L and P).
 ...
PMID:[Effect of prolonged consumption of lactose or hydrolyzed lactose in the rat. 2. Digestibility, retention and utilization of lactose components]. 708 7

It has been suggested that aspects of lactose consumption and metabolism favoring a relatively high tissue level of galactose-1-phosphate may predispose women to ovarian cancer. The authors sought to examine this hypothesis in a study of 108 18- to 74-year-old Caucasian residents of a three-county area of western Washington who were diagnosed with stage I ovarian cancer during 1989-1991, and 108 age- and race-matched controls. Lactose and galactose intake, measured using a food frequency questionnaire, had been hypothesized to increase risk, but were somewhat lower among the cases than among the controls (75th percentile of lactose intake vs. 25th: odds ratio (OR) = 0.80, 95% confidence interval (Cl) 0.52-1.2; of galactose intake: OR = 0.71, 95% Cl 0.48-1.1). Intestinal lactase activity, also hypothesized to have a positive relation with ovarian cancer occurrence, was measured with an oral lactose challenge followed by determination of urinary galactose; no evidence that it was related to the disease was found (75th percentile of excreted galactose vs. 25th: OR = 0.87, 95% Cl 0.62-1.2). Galactose-1-phosphate uridyltransferase (transferase), the enzyme responsible for the metabolism of galactose-1-phosphate, was measured in erythrocytes; no deficit in cases was observed (75th percentile of transferase activity vs. 25th: OR = 1.3, 95% Cl 0.80-2.1). There was also no excess of cases carrying low-activity genetic variants of the transferase enzyme (lower-activity variants vs. higher-activity variants: OR = 0.61, 95% Cl 0.21-1.7). These results do not support the hypothesis that aspects of lactose and galactose intake and metabolism have a bearing on the etiology of ovarian cancer.
 ...
PMID:Lactose and galactose intake and metabolism in relation to the risk of epithelial ovarian cancer. 787 85

Lactose consumption has been associated with a high incidence of cataract in northern Indian and southern Italian populations. Galactose absorbed after hydrolysis of lactose from milk in individuals with normal lactase activity is considered responsible. However, lactase-deficient subjects who often avoid drinking milk are able to digest lactose and absorb free galactose in fermented milk and yogurt. This study was conducted to evaluate the relationships between milk and yogurt consumption, galactose metabolism and cataract risk. Milk ingestion was dose-related with cataract risk in lactose digesters (particularly in diabetics) but not in lactose maldigesters. Conversely, yogurt intake had a protective dose-effect on cataract formation for the whole population. Maximal galactose concentrations after an oral galactose test increased exponentially with age. Red blood cell galactokinase activity was significantly lower in elderly subjects (> 60 y) than in young individuals (P < 0.05), and galactose-1-phosphate uridyl-transferase activity was significantly lower in institutionalized subjects and in home-living elderly with cataract than in healthy elderly subjects (P < 0.05). We conclude that the cataractogenic action of milk lactose is dependent on the disturbance of galactose metabolism in elderly subjects and that yogurt is not cataractogenic, although the mechanism of the protective effect of yogurt remains unknown.
 ...
PMID:Disturbed galactose metabolism in elderly and diabetic humans is associated with cataract formation. 833 7

Glucose Galactose Malabsorption is a genetic disorder caused by a defect in glucose and galactose transport across the intestinal brush border. Normally, lactose in milk is broken down into glucose and galactose by lactase, an ectoenzyme on the brush border, and the hexoses are transported into the cell by the Na+-glucose cotransporter SGLT1. The mutations causing the defect in sugar transport have been identified in patients from 33 kindreds, and functional studies have established how these mutations cause the disease.
 ...
PMID:I. Glucose galactose malabsorption. 981 14

Ovarian carcinoma is the fourth most common cause of cancer death in women. The cause and pathogenesis of this disease has remained obscure. Galactose, the hydrolyzing product of the milk sugar lactose, has been hypothesized to be toxic to ovarian epithelial cells and consumption of dairy products and lactase persistence has been suggested to be a risk factor for ovarian carcinoma. In adults, downregulation of lactase depends on a variant C/T-13910 at the 5' end of the lactase gene. To explore whether lactase persistence is related to the risk of ovarian carcinoma we determined the C/T-13910 genotype in a cohort of 782 women with ovarian carcinoma. The C/T-13910 genotype was defined by solid phase minisequencing from 327 Finnish, 303 Polish, 152 Swedish patients and 938 Finnish, 296 Polish and 97 Swedish healthy individuals served as controls. Lactase persistence did not associate significantly with increased risk for ovarian carcinoma in the Finnish (odds ratio [OR]=0.77, 95% confidence interval [CI]=0.57-1.05, p=0.097), in the Polish (OR=0.95, 95% CI=0.68-1.33, p=0.75), or in the Swedish populations (OR=1.63, 95% CI=0.65-4.08, p=0.29). Our results do not support the hypothesis that lactase persistence increases the ovarian carcinoma risk. On the contrary, lactase persistence may decrease the ovarian carcinoma risk at least in the Finnish population.
 ...
PMID:Lactase persistence and ovarian carcinoma risk in Finland, Poland and Sweden. 1588 May 73


1 2 Next >>