Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.20 (alpha-glucosidase)
 4,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bacterial periplasmic substrate-binding proteins are initial receptors in the process of active transport across cell membranes and/or chemotaxis. Each of them binds a specific substrate (e.g. sugar, amino acid, or ion) with high affinity. For transport, each binding protein interacts with a cognate membrane complex consisting of two hydrophobic proteins and two subunits of a hydrophilic ATPase. For chemotaxis, binding proteins interact with specific membrane chemotaxis receptors. We report, herewith, that the oligopeptide-binding protein OppA of Escherichia coli, the maltose-binding protein MalE of E. coli, and the galactose-binding protein MglB of Salmonella typhimurium interact with unfolded and denatured proteins, such as the molecular chaperones that are involved in protein folding and protein renaturation after stress. These periplasmic substrate-binding proteins promote the functional folding of citrate synthase and alpha-glucosidase after urea denaturation. They prevent the aggregation of citrate synthase under heat shock conditions, and they form stable complexes with several unfolded proteins, such as reduced carboxymethyl alpha-lactalbumin and unfolded bovine pancreatic trypsin inhibitor. These chaperone-like functions are displayed by both the liganded and ligand-free forms of binding proteins, and they occur at binding protein concentrations that are 10-100-fold lower than their periplasmic concentration. These results suggest that bacterial periplasmic substrate-binding proteins, in addition to their function in transport and chemotaxis, might be implicated in protein folding and protection from stress in the periplasm.
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PMID:Chaperone properties of the bacterial periplasmic substrate-binding proteins. 918 48

Elongation factor Tu (EF-Tu) is involved in the binding and transport of the appropriate codon-specified aminoacyl-tRNA to the aminoacyl site of the ribosome. We report herewith that the Escherichia coli EF-Tu interacts with unfolded and denatured proteins as do molecular chaperones that are involved in protein folding and protein renaturation after stress. EF-Tu promotes the functional folding of citrate synthase and alpha-glucosidase after urea denaturation. It prevents the aggregation of citrate synthase under heat shock conditions, and it forms stable complexes with several unfolded proteins such as reduced carboxymethyl alpha-lactalbumin and unfolded bovine pancreatic trypsin inhibitor. The EF-Tu.GDP complex is much more active than EF-Tu.GTP in stimulating protein renaturation. These chaperone-like functions of EF-Tu occur at concentrations that are at least 20-fold lower than the cellular concentration of this factor. These results suggest that EF-Tu, in addition to its function in translation elongation, might be implicated in protein folding and protection from stress.
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PMID:Chaperone properties of bacterial elongation factor EF-Tu. 956 60

Elongation factor G(EF-G) and initiation factor 2 (IF2) are involved in the translocation of ribosomes on mRNA and in the binding of initiator tRNA to the 30 S ribosomal subunit, respectively. Here we report that the Escherichia coli EF-G and IF2 interact with unfolded and denatured proteins, as do molecular chaperones that are involved in protein folding and protein renaturation after stress. EF-G and IF2 promote the functional folding of citrate synthase and alpha-glucosidase after urea denaturation. They prevent the aggregation of citrate synthase under heat shock conditions, and they form stable complexes with unfolded proteins such as reduced carboxymethyl alpha-lactalbumin. Furthermore, the EF-G and IF2-dependent renaturations of citrate synthase are stimulated by GTP, and the GTPase activity of EF-G and IF2 is stimulated by the permanently unfolded protein, reduced carboxymethyl alpha-lactalbumin. The concentrations at which these chaperone-like functions occur are lower than the cellular concentrations of EF-G and IF2. These results suggest that EF-G and IF2, in addition to their role in translation, might be implicated in protein folding and protection from stress.
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PMID:Chaperone properties of bacterial elongation factor EF-G and initiation factor IF2. 1062 18

A variety of milk proteins including lactoferrin, angiogenin-1, alpha-lactalbumin, beta-lactoglobulin, lactoperoxidase, casein and the novel whey proteins lactogenin and glycolactin were tested for inhibitory activity toward human immunodeficiency virus-1 reverse transcriptase (HIV-1 RT), alpha-glucosidase, beta-glucosidase and beta-glucuronidase. Lactoferrin exerted the most potent inhibitory action with an IC50 of about 6 microM. Lactoperoxidase, lactogenin, angiogenin-1 and glycolactin inhibited HIV-1 RT activity with decreasing potencies. Beta-lactoglobulin, alpha-lactalbumin and casein displayed little or no inhibitory effect. Succinylation with succinic anhydride augmented the inhibitory effect of glycolactin, beta-lactoglobulin, alpha-lactalbumin, casein and human lactoferrin. The inhibitory effect of the various milk proteins on the activities of alpha-glucosidase, beta-glucosidase and beta-glucuronidase was meager. Succinylation tended to increase the alpha-glucosidase-inhibitory effect of milk proteins but neither their beta-glucosidase-inhibitory nor beta-glucuronidase-inhibitory effect was affected.
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PMID:First demonstration of an inhibitory activity of milk proteins against human immunodeficiency virus-1 reverse transcriptase and the effect of succinylation. 1110 90

Thioredoxin, thioredoxin reductase and NADPH form the thioredoxin system and are the major cellular protein disulphide reductase. We report here that Escherichia coli thioredoxin and thioredoxin reductase interact with unfolded and denatured proteins, in a manner similar to that of molecular chaperones that are involved in protein folding and protein renaturation after stress. Thioredoxin and/or thioredoxin reductase promote the functional folding of citrate synthase and alpha-glucosidase after urea denaturation. They also promote the functional folding of the bacterial galactose receptor, a protein without any cysteines. Furthermore, redox cycling of thioredoxin/thioredoxin reductase in the presence of NADPH and cystine stimulates the renaturation of the galactose receptor, suggesting that the thioredoxin system functions like a redox-powered chaperone machine. Thioredoxin reductase prevents the aggregation of citrate synthase under heat-shock conditions. It forms complexes that are more stable than those formed by thioredoxin with several unfolded proteins such as reduced carboxymethyl alpha-lactalbumin and unfolded bovine pancreatic trypsin inhibitor. These results suggest that the thioredoxin system, in addition to its protein disulphide isomerase activity possesses chaperone-like properties, and that its thioredoxin reductase component plays a major role in this function.
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PMID:Chaperone properties of Escherichia coli thioredoxin and thioredoxin reductase. 1254 77

We have cloned, purified to homogeneity, and characterized as a molecular chaperone the Escherichia coli YedU protein. The purified protein shows a single band at 31 kDa on SDS-polyacrylamide gels and forms dimers in solution. Like other chaperones, YedU interacts with unfolded and denatured proteins. It promotes the functional folding of citrate synthase and alpha-glucosidase after urea denaturation and prevents the aggregation of citrate synthase under heat shock conditions. YedU forms complexes with the permanently unfolded protein, reduced carboxymethyl alpha-lactalbumin. In contrast to DnaK/Hsp70, ATP does not stimulate YedU-dependent citrate synthase renaturation and does not affect the interaction between YedU and unfolded proteins, and YedU does not display any peptide-stimulated ATPase activity. We conclude that YedU is a novel chaperone which functions independently of an ATP/ADP cycle.
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PMID:Characterization of the Escherichia coli YedU protein as a molecular chaperone. 1256 79

The aim of this study was to obtain information that could help to ease the weaning transition in commercial pig production. Before weaning, phytohemagglutinin (PHA) in the form of a crude preparation of red kidney bean lectin was fed by gavage to 24 crossbred [(Swedish Landrace x Yorkshire) x Hampshire] piglets, whereas 24 control piglets were fed alpha-lactalbumin by gavage, to study the effect on growth, occurrence of postweaning diarrhea, feeding behavior, and some anatomical and physiological traits of the gastrointestinal tract. Within the litter, piglets were randomly assigned to PHA treatment or control and remained in the same pen from the beginning (PHA exposure at 7 d before weaning) until the end of the experiment (14 d post-weaning). Weaning took place at the age of 31 to 34 d. Pigs treated with PHA grew faster (P = 0.013) during the first week postweaning and tended to have lower total diarrhea scores (P = 0.10) than did control pigs. On d 5 after weaning, piglets treated with PHA spent more time eating (P = 0.028) than control pigs. No immunostimulating effect of PHA, measured by plasma immunoglobulin G, could be detected. An increase in the intestinal barrier properties before weaning, as a response to PHA treatment, was demonstrated in intestinal absorption studies using Na-fluorescein and BSA as gavage-fed markers. Less uptake (measured as plasma concentrations) of the marker molecule Na-fluorescein occurred during a 24-h study period, and numerically lower levels of BSA were observed compared with studies in control pigs of the same age. A total of 12 pigs (6 control, 6 PHA-treated) were euthanized on the day of weaning for analyses of gastrointestinal properties. The PHA-treated pigs tended to have a longer total small intestinal length (P = 0.063) than that of the control pigs. The enzyme profile of the jejunal epithelium responded to PHA exposure with a decrease in lactase activity and an increase in maltase and sucrase activities, which is similar to changes normally observed after weaning. No differences were found in the size of the pancreas or in its contents of trypsin and amylase. In conclusion, exposing piglets to crude, red kidney bean lectin for 3 d during the week before weaning led to changes in performance and small intestinal functional properties that would be expected to contribute to a more successful weaning.
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PMID:Effects of crude red kidney bean lectin (phytohemagglutinin) exposure on performance, health, feeding behavior, and gut maturation of pigs at weaning. 1704 Sep 48

We investigated whether bovine milk constituents influenced glucagon-like peptide (GLP)-2 secretion and intestinal growth in suckling rats. Male Sprague-Dawley rats (14 d old) received i.g. infusions of a milk protein fraction, a lactose solution, or the cream fraction of milk. The serum concentration of GLP-2, but not GLP-1, markedly increased in rats administered milk protein compared with those given the lactose solution or the cream fraction from 60 to 120 min after administration. In another experiment, both casein (CN) and whey protein isolate stimulated GLP-2 secretion at 120 min after administration, but soy protein and ovalbumin did not. Stimulation of GLP-2 secretion by several milk proteins was similar, including alpha-CN, alpha-lactalbumin (alpha-La), and beta-lactoglobulin, in a separate experiment. A hydrolysate of alpha-La obtained by incubation with protease A extracted from Aspergillus oryzae (LaHPA) caused almost twice the GLP-2 release due to intact alpha-La and other alpha-La hydrolysates. Free amino acid concentrations and molecular size distributions did not differ among alpha-La hydrolysates, including LaHPA. In rat pups reared with milk formulae containing alpha-La or LaHPA, LaHPA significantly promoted small intestinal elongation and increased the number of crypt epithelial cells compared with a formula containing intact alpha-La. LaHPA administration also increased the maltase:lactase activity ratio, a marker of maturation of the intestinal mucosa. In conclusion, milk proteins stimulate GLP-2 secretion and contribute to growth and maturation of the small intestine in suckling rats.
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PMID:alpha-Lactalbumin hydrolysate stimulates glucagon-like peptide-2 secretion and small intestinal growth in suckling rats. 1949 23