Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Two alpha-glucosidase (maltase) genes, designated GLUCPI and GLUCPII, have been cloned from an industrial strain of baker's yeast (Saccharomyces cerevisiae) by complementation of a maltase-negative mutant strain. The different genes were identified according to their alternatively expressed isoenzymes PI and PII in transformants after isoelectric focusing and activity staining in separated cell lysates. The gene encoding alpha-glucosidase PI (GLUCPI), which was not present in laboratory strains of S. carlsbergensis with a defined MAL1, 2, 3, 4 or 6 locus, was sequenced and compared with the recently published MAL6S gene. This comparison revealed single amino acid deviations at three positions in the predicted polypeptide sequence. In addition, the divergent promoter region of GLUCPI differed from MAL6S by a triple repeated 147-bp DNA segment. Maltose induction and glucose repression of alpha-glucosidase PI were not affected by the deletion of the repeated DNA segment. However, the absolute expression of alpha-glucosidase PI increased two- to four-fold. In addition, a two-fold increase in the maltase synthesis occurred when the cloned positive regulator gene MAL2-8ep was on the same plasmid. Furthermore, stability of the alpha-glucosidase in cultures in the stationary growth phase was greatly enhanced using a host strain lacking the proteinases A and B and the carboxypeptidases Y and S. Promoter trimming, MAL2-8cp stimulation and the use of a host strain deficient in four vacuolar proteinases resulted in alpha-glucosidase PI expression of about 13% of the soluble protein.
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PMID:Cloning and characterization of baker's yeast alpha-glucosidase: over-expression in a yeast strain devoid of vacuolar proteinases. 264 95

To study the effects of acarbose, an alpha-glucosidase inhibitor, on saccharide absorption and pancreatic and gut hormone release, we loaded 50 g glucose (GTT), maltose (MTT), and sucrose (STT) to 12 healthy male volunteers with and without acarbose (0, 100, or 300 mg) in a double-blind protocol. Oral load of 300 mg acarbose did not inhibit absorption of 50 g glucose; neither did it alter subsequent responses of insulin and glucagons. Maltose absorption was not influenced by acarbose up to 300 mg. However, insulin response was reduced and eteroglucagon response was enhanced by acarbose. Acarbose 100 mg markedly decreased absorption of sucrose, resulting in inhibition of plasma elevation of glucose and insulin and in enhancement of enteroglucagon release. Oral load of 30 g lactulose, nonabsorbable disaccharide, could reproduce the acarbose-induced enteroglucagon release. An increase in osmotic pressure due to retention of unabsorbed carbohydrate in the distal small intestine and proximal colon may explain the acarbose-induced enteroglucagon release and diarrhea that results from STT with acarbose.
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PMID:Enteroglucagon release in disaccharide malabsorption induced by intestinal alpha-glucosidase inhibition. 265 36

Toluene-treated cells of Streptococcus bovis JB1 phosphorylated cellobiose, glucose, maltose, and sucrose by the phosphoenolpyruvate-dependent phosphotransferase system. Glucose phosphorylation was constitutive, while all three disaccharide systems were inducible. Competition experiments indicated that separate phosphotransferase systems (enzymes II) existed for glucose, maltose, and sucrose. [14C]maltose transport was inhibited by excess (10 mM) glucose and to a lesser extent by sucrose (90 and 46%, respectively). [14C]glucose and [14C]sucrose transports were not inhibited by an excess of maltose. Since [14C]maltose phosphorylation in triethanolamine buffer was increased 160-fold as the concentration of Pi was increased from 0 to 100 mM, a maltose phosphorylase (Km for Pi, 9.5 mM) was present, and this activity was inducible. Maltose was also hydrolyzed by an inducible maltase. Glucose 1-phosphate arising from the maltose phosphorylase was metabolized by a constitutive phosphoglucomutase that was specific for alpha-glucose 1-phosphate (Km, 0.8 mM). Only sucrose-grown cells possessed sucrose hydrolase activity (Km, 3.1 mM), and this activity was much lower than the sucrose phosphotransferase system and sucrose-phosphate hydrolase activities.
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PMID:Transport and phosphorylation of disaccharides by the ruminal bacterium Streptococcus bovis. 282 69

Maltose fermentation in Saccharomyces carlsbergensis is dependent upon the MAL6 locus. This complex locus is composed of the MAL61 and MAL62 genes, which encode maltose permease and maltase, respectively, and a third gene, MAL63, which codes for a trans-acting positive regulatory product. In wild-type strains, expression of the MAL61 and MAL62 mRNAs and proteins is induced by maltose and induction is dependent upon the MAL63 gene. Mutants constitutively expressing the MAL61 and MAL62 gene products have been isolated in mal63 backgrounds, and the mutations which have been analyzed map to a fourth MAL6-linked gene, MAL64. Cloning and characterization of this new gene are described in this report. The results revealed that the MAL64-C alleles present in constitutive strains encode a trans-acting positive function required for constitutive expression of the MAL61 and MAL62 gene products. In inducible strains, the MAL64 gene is dispensable, as deletion of the gene had no effect on maltose fermentation or maltose-regulated induction. MAL64 encoded transcripts of 2.0 and 1.4 kilobase pairs. While both MAL64 mRNAs were constitutively expressed in constitutive strains, they were maltose inducible in wild-type strains and induction was dependent upon the MAL63 gene. The MAL63 and MAL64 genes are at least partially structurally homologous, suggesting that they control MAL61 and MAL62 transcript accumulation by similar mechanisms.
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PMID:Constitutive expression of the maltose fermentative enzymes in Saccharomyces carlsbergensis is dependent upon the mutational activation of a nonessential homolog of MAL63. 283 55

Both the MAL1 and MAL6 loci in Saccharomyces strains have been shown by functional and structural studies to comprise a cluster of at least three genes necessary for maltose utilization. They include regulatory, maltose transport and maltase genes designated MALR, MALT and MALS, respectively. Subclones of each gene derived from the MAL6 locus were inserted into the multicopy shuttle plasmid YEp13, introduced into MAL1 and mal1 strains and the effects of altered gene dosage of each gene, or a combination of them, on MAL gene expression investigated. MAL1 strains transformed with a plasmid carrying the MAL6S gene showed coordinate four to five fold increases in both maltase enzyme activity and its mRNA, whereas no increase in maltose transport activity or of MALT mRNA was observed when MAL6T was present on multicopy plasmids. The presence of the MAL6R gene on a multicopy plasmid led to greatly increased transcription of both inducible and constitutive mRNAs with homology to the regulatory gene; it also gave rise to two fold increases in both induced maltase mRNA levels and enzyme activity, but only in the presence of maltose. However, it had no apparent effect on the accumulation of MALT mRNA. Finally, the induction kinetics of plasmid-borne and chromosomal MALS and MALT gene expression were examined under conditions of altered gene dosage of the MAL6 regulatory and structural genes. The results of these experiments indicate that MALR encodes a trans-acting positive activator that requires maltose for induction of MALS and MALT transcription even when the regulatory gene is present on a multicopy plasmid. Maltose transport can be a rate-limiting factor in MAL gene expression, at least in the early stages of induction. The regulation of the MALS and MALT genes, whose activities are coordinately induced in MAL1 strains by maltose, may in fact exhibit some important differences.
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PMID:Regulation of MAL gene expression in yeast: gene dosage effects. 332 27

Maltose fermentation in Saccharomyces spp. requires the presence of a dominant MAL locus. The MAL6 locus has been cloned and shown to encode the structural genes for maltose permease (MAL61), maltase (MAL62), and a positively acting regulatory gene (MAL63). Induction of the MAL61 and MAL62 gene products requires the presence of maltose and the MAL63 gene. Mutations within the MAL63 gene produce nonfermenting strains unable to induce the two structural gene products. Reversion of these mal63 nonfermenters to maltose fermenters nearly always leads to the constitutive expression of maltase and maltose permease, and constitutivity is always linked to MAL6. We demonstrated that for one such revertant, strain C2, constitutivity did not require the MAL63 gene, since deletion disruption of this gene did not affect the constitutive expression of the structural genes. In addition, constitutivity was trans acting. Deletion disruption of the MAL6-linked structural genes for maltase and maltose permease in this strain did not affect the constitutive expression of a second, unlinked maltase structural gene. We isolated new maltose-fermenting revertants of a nonfermenting strain which carried a deletion disruption of the MAL63 gene. All 16 revertants isolated expressed maltase constitutively. In one revertant studied in detail, strain R10, constitutive expression was demonstrated to be linked to MAL6, semidominant, trans acting, and residing outside the MAL63-MAL61-MAL62 genes. From these studies we propose the existence of a second trans-acting regulatory gene at the MAL6 locus. We call this new gene MAL64. We mapped the MAL64 gene 2.3 centimorgans to the left of MAL63. The role of the MAL64 gene product in maltose fermentation is discussed.
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PMID:Identification of a second trans-acting gene controlling maltose fermentation in Saccharomyces carlsbergensis. 353 26

Spores of the fungus Myrothecium verrucaria are cryptic to maltose and isomaltose. Induction of a transport system can be effected by several sugars whose order of effectiveness is: turanose > maltulose > sucrose > d-arabinose, d-fructose, nigerose, maltotriulose, kestose > melezitose, raffinose, nystose, and stachyose. The transport system is not specific to maltose and isomaltose, and it is apparently identical to an induced trehalose permease described previously. Induction of the permease is markedly influenced by spore age-older spores being more responsive. Pure maltose is not absorbed by spores. Absorption of commercial reagent-grade maltose is due to permease induction by maltulose as an impurity. Maltulose contamination of maltose was demonstrated by charcoal column chromatography and comparison of its physical, chemical, and permease-inductive properties with those of authentic maltulose. Maltose accumulates temporarily in spores after absorption and then decreases, although no conversion to glucose can be detected. Although spores contain small quantities of maltase, metabolism of maltose may be via some nonhydrolytic pathway.
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PMID:Crypticity of Myrothecium verrucaria spores to maltose and induction of transport by maltulose, a common maltose contaminant. 569 Sep 32

The activity of enzymes releasing glucose and reducing sugars from sucrose, maltose, starch and dextran was compared in the same pooled samples of plaque fluid (PF) from 24 h human dental plaque. Equimolar amounts of glucose and fructose were released from sucrose in 3 h incubations. Reducing activity was released from sucrose or starch at a similar rate. The rate of glucose release from the starch substrate was similar to that from maltose but lower than that from sucrose. Raffinose was hydrolysed, indicating beta-fructosidase activity in PF. The hydrolysis of maltose, trehalose and melezitose confirmed the presence of alpha-glucosidase activity. Maltose was metabolized partially to a maltosaccharide. No dextranase activity was detectable in PF, and the soluble polymeric carbohydrate in PF was partially degraded by fungal dextranase. Starch was degraded to dextrins, maltose and glucose.
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PMID:Hydrolysis of some carbohydrate substrates by enzymes of pooled human dental plaque fluid. 617 18

Maltose fermentation in Saccharomyces spp. requires the presence of any one of five unlinked genes: MAL1, MAL2, MAL3, MAL4, or MAL6. Although the genes are functionally equivalent, their natures and relationships to each other are not known. At least three proteins are necessary for maltose fermentation: maltase, maltose permease, and a regulatory protein. The MAL genes may code for one or more of these proteins. Recently a DNA fragment containing a maltase structural gene has been cloned from a MAL6 strain, CB11, to produce plasmid pMAL9-26. We have conducted genetic and physical analyses of strain CB11. The genetic analysis has demonstrated the presence of two cryptic MAL genes in CB11, MAL1g and MAL3g (linked to MAL1 and to MAL3, respectively), in addition to the MAL6 locus. The physical analysis, which used a subclone of plasmid pMAL9-26 as a probe, detected three HindIII genomic fragments with homology to the probe. Each fragment was shown to be linked to one of the MAL loci genetically demonstrated to be present in CB11. Our results indicate that the cloned maltase structural gene in plasmid pMAL9-26 is linked to MAL6. Since the MAL6 locus has previously been shown to contain a regulatory gene, the MAL6 locus must be a complex locus containing at least two of the factors needed for maltose fermentation: the structural gene for maltase and the maltase regulatory protein. The absence of other fragments which hybridize to the MAL6-derived probe shows that either MAL2 and MAL4 are not related to MAL6, or the DNA corresponding to these genes is absent from the MAL6 strain CB11.
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PMID:Repeated family of genes controlling maltose fermentation in Saccharomyces carlsbergensis. 634 55

To determine the extent of maltose excreted into the urine, sugar substances present in the urine following intravenous infusion of maltose were analyzed. Maltose, glucose, maltotriose and maltotetraose in the urine were detected by gas chromatography and identified by mass spectrometric analysis. The total amounts of sugar substances excreted after 10 per cent maltose solution given at three different infusion rates were calculated. The excreted amounts of maltotriose and maltotetraose increased in a dose and time dependent manner. As these compounds were not detected in the plasma either during or after the administration of maltose, the kidney probably plays a role in the biosynthesis of maltotriose and maltotetraose. Studies on the organ homogenates of the rabbit showed that the enzyme activity for the biosynthesis of maltotriose from maltose was mainly in the kidney. The glucose excreted into the urine probably originates from maltose catalyzed to glucose, mainly by the action of kidney maltase. As the rate of excretion of sugar substances increased in a dose dependent manner, adequate infusion rates of maltose should be less than 0.5 g/kg/hour.
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PMID:Maltotriose and maltotetraose excreted in urine following intravenous administration of maltose to human volunteers. 664 21


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