Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The thermal stability of enzymes lactase and invertase in dried, amorphous matrices of sugars (trehalose, maltose, lactose, sucrose, raffinose) and some other selected systems (casein, PVP, milk) was studied. The glass transition temperature (Tg) was limited as a threshold parameter for predicting enzyme inactivation because (a) enzyme inactivation was observed in glassy matrices, (b) a specific effect of enzyme stabilization by certain matrices particularly trehalose was observed, and (c) enzyme stability appeared to depend on heating temperature (T) "per se" rather than (T-Tg). For these reasons, a protective mechanism by sugars related to the maintenance of the tertiary structure of the enzyme was favored. A rapid loss of enzyme (lactase) activity was observed in heated sucrose systems at T > Tg, and this was attributed to sucrose crystallization since it is known that upon crystallization the protective effect of sugars is lost. Thus, the stabilizing effect could be indirectly affected by the Tg of the matrix, since crystallization of sugars only occurs above Tg. Trehalose model systems (with added invertase) showed an exceptional stability toward "darkening" (e.g., non-enzymatic browning) when heated in the dried state to elevated temperatures and for long periods of time.
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PMID:Glassy state and thermal inactivation of invertase and lactase in dried amorphous matrices. 941 44

Biosensors for the determination of glucose, sucrose and lactose were based on a Clark-type oxygen electrode covered with a membrane containing microbial cells. The glucose-sensing membrane was prepared with intact cells of Gluconobacter oxydans immobilized in gelatin cross-linked with glutardialdehyde. The disaccharide-sensing membranes were prepared by co-immobilization of G. oxydans with cells of Saccharomyces cerevisiae containing invertase for sucrose determination and with permeabilized cells of Kluyveromyces marxianus containing beta-galactosidase for lactose determination. The strain of G. oxydans that we used was able to oxidize both anomers of glucose at the same rate; there was therefore no need for mutarotase co-immobilization in disaccharide-sensing membranes. The sensitivity of glucose sensor was 50 nA/mM, the range of the calibration curve was 0-0.8 mM, the response time was 2 min, and the response after 1 week of storage was 62% of the initial response. The parameters of the disaccharide sensors were similar: linear range of calibration curve up to 4 mM, response time 5 min. The activities of the sensors after 1 week of storage at ambient temperature were in the range 50-65% of the initial activity.
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PMID:Microbial cell-based biosensor for sensing glucose, sucrose or lactose. 956 11

The hypoglycemic effect and the alpha-glucosidase activity inhibition of acarbose (AC:alpha-glucosidase inhibitor) were investigated in normal and KK-Ay mice, an animal model of noninsulin-dependent diabetes mellitus (NIDDM). AC improved hyperglycemia after an oral administration of maltose or sucrose, dose dependently in normal mice (1, 10, and 50mg/kg body weight) and in KK-Ay mice (50mg/kg). Furthermore, AC (50mg/kg) significantly inhibited maltase and sucrase activities in the small intestines of normal and KK-Ay mice (inhibitory efficacy: sucrase > maltase). The enzymatic inhibition in KK-Ay mice is stronger than in normal mice. However, AC (50 mg/kg) did not suppress the blood glucose in oral lactose tolerance and did not inhibit the lactase activity in either normal or KK-Ay mice. These findings indicate that the AC effect on the inhibition of alpha-glucosidase activity is selective for sucrase and maltase in normal and NIDDM mice.
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PMID:Effect of acarbose (alpha-glucosidase inhibitor) on disaccharase activity in small intestine in KK-Ay and ddY mice. 974 58

At weaning, mammals switch from milk to complex adult food, and change from a lactose-rich to a lactose-free diet. At the same time, the small intestine matures resulting in changes in lactase expression and the onset of sucrase. The aim of this study was to analyze the effect of premature and specific depletion of lactose on maturation of the small intestine and on lactase expression in suckling mice. For this purpose, from postnatal days 10 to 16, suckling mice were fed by transgenic alpha-lactalbumin-deficient females that produce lactose-free milk. Pups fed with lactose-free milk had a lower body weight than controls fed by wildtype females. They also displayed hypotrophy of intestinal muscle layers, but no obvious alterations in the morphology of the intestinal epithelium. The level of lactase activity as well as the longitudinal distribution of corresponding mRNA were unchanged compared to suckling animals nourished with normal lactose-containing milk. Finally, there was no premature onset of sucrase expression. We conclude that feeding suckling mice for six days with lactose-free milk does not provoke any premature maturation of the small intestine. Thus, decreasing lactose intake is not a major cause for the modifications of lactase expression which occur at weaning.
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PMID:Lactase is unchanged in suckling mice fed with lactose-free milk. 988 Dec 68

We investigated the effect of an intermittent feeding schedule on the development of disaccharidase activities in the small intestine of artificially reared (AR) rat pups. Rat pups were fitted with an intragastric cannula at 5 days of age. A milk formula similar to the composition of rat milk was supplied by intermittent gastric infusion over the following 15-19 days. The body weight gain and plasma corticosterone levels of the AR pups matched those of pups reared naturally by dams (MR pups). At 10, 15 and 19 days of age, the small intestine from the ligament to Treitz to the ileocecal junction was divided into three segments of equal length and enzyme activities were measured in each. At the age of 10 and 15 days, sucrase and isomaltase activities were undetectable in AR pups fed according to a controlled schedule from the early postnatal period. These activities were first detected in the middle segment of the small intestine at 9 days of age in both AR and MR pups. Sucrase and isomaltase activities at the age of 19 days were diurnal in AR pups, but arrhythmic in MR pups. We conclude that artificial rearing via the intermittent gastric infusion of a milk formula containing only lactose as the carbohydrate source did not prematurely increase intestinal sucrase and isomaltase activities. Diurnal changes started from the beginning of development of these enzyme activities in AR pups.
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PMID:Effect of intermittent feeding on the development of disaccharidase activities in artificially reared rat pups. 997 25

Enzymatic changes are often detrimental to quality of low-moisture foods. In the present study, effects of glass transition and water on sucrose inversion in a lactose-sucrose food model were investigated. Amorphous samples were produced by freeze-drying lactose-sucrose (2:1)-invertase (20 mg invertase/49.4 g of carbohydrate) dissolved in distilled water. Sorption isotherms were determined gravimetrically at 24 degrees C. Sucrose hydrolysis was determined by monitoring glucose content using a test kit and the amounts of fructose, glucose, and sucrose using HPLC. The glass transition temperatures, T(g), at various water contents were measured using differential scanning calorimetry (DSC). The BET and the GAB sorption models were fitted to experimental data up to a(w) 0.444 and 0.538, respectively. Water sorption and DSC results suggested time-dependent crystallization of sugars at a(w) 0.444 and above. Significant sucrose hydrolysis occurred only above T(g), concomitantly with crystallization. Sucrose hydrolysis and crystallization were not likely in glassy materials.
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PMID:Glass transition and water effects on sucrose inversion by invertase in a lactose-sucrose system. 1088 68

Lactosucrose synthesis from sucrose and lactose was carried out by using beta-fructofuranosidase from Arthrobacter sp. K-1. The transfructosylation mechanism was found to be of an ordered bi-bi type in which sucrose was bound first to the enzyme and lactosucrose was released last. Hydrolysis side-reaction experiments indicated that the reactions were uncompetitively inhibited by glucose and lactose, while no inhibition by fructose was apparent. The overall reaction rates were formulated. The reaction rate constants, equilibrium constant, and dissociation and Michaelis constants were determined at 35 degrees C and 50 degrees C by fitting the experimental concentration changes with the calculated values by a nonlinear least-square method. The average relative derivation for the concentrations was 9.67%. The kinetic parameters were also calculated for 43 degrees C and 60 degrees C by assuming the Arrhenius law, and the course of reaction was predicted. The obtained reaction rate equations well represented the concentration changes during the experiment at all temperatures.
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PMID:Reaction kinetics and modeling of the enzyme-catalyzed production of lactosucrose using beta-fructofuranosidase from Arthrobacter sp. K-1. 1138 50

The effect of source of carbohydrate on gut histology, digestion efficiency, and growth performance in early-weaned (25 d) rabbits at the starter period (25 to 39 d) was investigated. Six diets were factorially arranged to study the effect of partial substitution of starch (0, 25, or 50%) by lactose at two levels of fiber (30 or 36% NDF). Diets were formulated to meet or exceed essential nutrient requirements of growing rabbits. A feeding trial was conducted to measure the effect of treatments on growth performance in 252 rabbits that were fed the experimental diets in the starter period and thereafter received a common feed until 60 d of age. Fecal apparent digestibility was determined at 35 d of age in nine animals per diet. The four diets with extreme lactose content were used to determine ileal apparent digestibility of starch and lactose (nine replicates per diet), weights of stomach and cecum, stomach pH, cecal fermentation traits, amylase and disaccharidase activities (10 animals per diet), and jejunal morphology (six animals per diet). Weaning increased (P < 0.001) amylase activity by 59% but decreased (P < 0.001) maltase, sucrase, and lactase activities by 30, 48, and 72%, in parallel with a reduction of villus height by 19%. Dietary NDF level did not affect either jejunal morphology or sucrase and lactase activities but increased amylase (P = 0.05) and maltase (P < 0.001) activities by 22 and 92%, respectively. Substitution of starch by lactose had no effect on jejunal morphology or enzymatic activity. Ileal lactose and starch digestibility were not affected by dietary NDF or lactose level and averaged 73.8 and 90.8%, respectively. Substitution of starch by fiber and lactose affected ileal flux of starch plus lactose (by -0.5 and +1.7 g/d) and cecal pH (by +2.1 and -2.8%, respectively). Fecal NDF digestibility was relatively low (23.1% on average) and was not affected by treatments, whereas that of lactose and starch was almost complete. An increase of dietary NDF level led to an impairment of ADG and feed efficiency in the starter (P < 0.002) and in the overall (P < 0.03) fattening period. Substitution of starch by lactose linearly decreased (P < 0.001) feed efficiency in the starter period and linearly increased (P < 0.001) diarrhea incidence in the fattening period. The results indicate that digestive capability of early-weaned rabbits is limited and should be taken into account to establish optimal levels and sources of carbohydrates in the starter diet.
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PMID:Effect of levels of starch, fiber, and lactose on digestion and growth performance of early-weaned rabbits. 1200 9

In terms of maximum extractable catalytic activity, sucrose synthase is the predominant sucrolytic enzyme in developing cotyledons of faba bean (Vicia faba L.). Although acid invertase activity is extremely low, there is significant activity of alkaline invertase, the majority of which is extractable only with high concentrations of NaCl. Calculations of potential activity in vivo indicate that alkaline invertase is the predominant sucrolytic enzyme from 50 days after anthesis onward. However, at almost all stages of cotyledon development analyzed, the maximum extractable catalytic activities of both enzymes is in excess of the actual rate of starch deposition. Two forms of alkaline invertase were identified in developing cotyledons. The major form has been purified to homogeneity, and antibodies have been raised against it. The native protein has a molecular mass of about 238 [plus or minus] 4.5 kD. It is apparently a homotetramer (subunit molecular mass 53.4 [plus or minus] 0.9 kD). The enzyme has a pH optimum of 7.4, an isoelectric point of 5.2, and a Km[sucrose] of 10 mM and is inhibited by Tris (50% inhibition at 5 mM) and fructose (30% inhibition at 10 mM). Bean alkaline invertase is a [beta]-fructofuranosidase with no significant activity against raffinose, stachyose, trehalose, maltose, or lactose.
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PMID:Sucrolytic Enzyme Activities in Cotyledons of the Faba Bean (Developmental Changes and Purification of Alkaline Invertase). 1222 91

A genetic locus that is adjacent to the gene encoding the small acid-soluble protein SASP C-4 of Bacillus megaterium has been identified. This locus, designated fru, contains a beta-fructosidase gene (fruA), a gene encoding a hydrophobic protein that is closely related to non-PTS sugar permeases of the proton symport type (fruP), and a gene coding for a transcriptional regulator of the LacI/GalR family (fruR). The FruA protein can hydrolyze sucrose and raffinose, but not maltose, isomaltose, trehalose, melibiose or lactose. The transcription initiation site of fruP has been mapped and the fruP promoter identified. Gel mobility shift assays showed that the FruR protein can bind specifically to a DNA fragment containing the fruP promoter region. DNase I footprinting analysis has defined the FruR binding site. Disruption of fruR led to high-level constitutive expression of fruPA, but had no effect on expression from the fruR promoter itself, indicating that FruR acts as a repressor of fruPA expression, but does not autoregulate its own synthesis. Interestingly, expression of fruPA in B. megaterium was not induced by sucrose, raffinose, fructose or inulin, whereas the constitutive expression of fruPA in a fruR mutant was repressed by both glucose and sucrose. Possible physiological implications of these findings are discussed.
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PMID:Identification and characterization of the non-PTS fru locus of Bacillus megaterium ATCC 14581. 1239 98


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