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)

A selection system has been devised for isolating hexokinase PII structural gene mutants that cause defects in carbon catabolite repression, but retain normal catalytic activity. We used diploid parental strains with homozygotic defects in the hexokinase PI structural gene and with only one functional hexokinase PII allele. Of 3,000 colonies tested, 35 mutants (hex1r) did not repress the synthesis of invertase, maltase, malate dehydrogenase, and respiratory enzymes. These mutants had additional hexokinase PII activity. In contrast to hex1 mutants (Entian et al., Mol. Gen. Genet. 156:99-105, 1977; F.K. Zimmermann and I. Scheel, Mol. Gen. Genet. 154:75-82, 1977), which were allelic to structural gene mutants of hexokinase PII and had no catalytic activity (K.-D. Entian, Mol. Gen. Gent. 178:633-637, 1980), the hex1r mutants sporulated hardly at all or formed aberrant cells. Those ascospores obtained were mostly inviable. As the few viable hex1r segregants were sterile, triploid cells were constructed to demonstrate allelism between hex1r mutants and hexokinase PII structural gene mutants. Metabolite concentrations, growth rate, and ethanol production were the same in hex1r mutants and their corresponding wild-type strains. Recombination of hexokinase and glucokinase alleles gave strains with different specific activities. The defect in carbon catabolite repression was strongly associated with the defect in hexokinase PII and was independent of the glucose phosphorylating capacity. Hence, a secondary effect caused by reduced hexose phosphorylation was not responsible for the repression defect in hex1 mutants. These results, and those with the hex1r mutants isolated, strongly supported our earlier hypothesis that hexokinase PII is a bifunctional enzyme with (i) catalytic activity and (ii) a regulatory component triggering carbon catabolite repression (Entian, Mol. Gen. Genet. 178:633-637, 1980; K.-D. Entian and D. Mecke, J. Biol. Chem. 257:870-874, 1982).
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PMID:Saccharomyces cerevisiae mutants provide evidence of hexokinase PII as a bifunctional enzyme with catalytic and regulatory domains for triggering carbon catabolite repression. 637 Sep 59

Fermentation of maltose by Saccharomyces strains depends on the presence of any one of five unlinked MAL loci (MAL1, MAL2, MAL3, MAL4 or MAL6). Earlier mutational analyses of MAL2 and MAL6 containing strains have identified a single complementation group at each of these two loci. However complementation analysis between naturally occurring Mal- Saccharomyces strains isolated from the wild demonstrated the presence of two complementation groups (designated MALp and MALg) at the MAL1, MAL3 and MAL6 loci. The available evidence suggests that the MALp gene is functionally equivalent to the complementation group identified by mutational analysis at the MAL6 locus and that this gene encodes a protein involved in the regulation of the coordinate induction of both maltase and maltose permease synthesis. In this paper we report the isolation, in a well characterized MAL1 strain, of 47 mutants unable to ferment maltose. All the mutants, with one exception, map at the MAL1 locus. These mal1 mutants, except for one, are recessive to MAL1 and fall into two major complementation groups. Evidence is presented that these two classes of mutants identify both a gene involved in the regulation of maltose identify both a gene involved in the regulation of maltose fermentation (MAL1R) and a gene involved in maltose transport (MAL1T). We also report here the isolation of a temperature sensitive maltose nonfermenting mutant mapping at the MAL1 locus identifying a third gene (MAL1S) at this locus. The maltase synthesized by this mutant, when assayed in cell-free extracts, is significantly more thermolabile than the wild type enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Gen Genet 1984
PMID:Mutational analysis of the MAL1 locus of Saccharomyces: identification and functional characterization of three genes. 638 96

Yeast DNA pools were prepared by ligating partial Sau3A genomic digests from strains carrying various MAL genes into the BamHI site of the yeast-Escherichia coli shuttle vector YRp7. They were used to transform recipient yeast strains that could not utilize maltose since they lacked a classical MAL gene. Transformants were obtained that could use maltose and also formed normal levels of maltase. They were unstable. They would lose the selective marker TRP1 of YRp7 alone, together with the ability to utilize maltose or only the ability to utilize maltose. The insertion of one of the plasmids was used as a hybridization probe for the others and found to share homologous sequences with all. They were then shown to contain the replication origin of the yeast 2 micron circle plasmid and additional sequences. These additional sequences were used to probe genomic digests of total yeast DNA. They hybridized at various degrees of efficiency with several bands, indicating that they were part of a family of repeated sequences. Apparently, it was the combination of the replication origin of the 2 micron circles with the additional sequences that promoted maltose utilization.
Mol Gen Genet 1984
PMID:A hybrid DNA sequence containing the replication origin of the multicopy yeast plasmid 2 micron circle and an additional repeated sequence can convert maltose-negative into maltose-positive strains. 639 95

Mutants with reduced hexokinase activity previously isolated as resistant to carbon catabolite repression of invertase and maltase (Zimmermann and Scheel, 1977) were allele tested with mutant strains of Lobo and Maitra (1977) which had defects in one or several of the genes coding for glucokinase and the two unspecific hexokinases. It could be demonstrated, that the mutation abolishing carbon catabolite repression had occurred in a gene allelic to the structural gene of hexokinase PII. Moreover, the defective mutant allele for hexokinase PII isolated by Lobo and Maitra (1977) was also defective in carbon catabolite repression. Neither glucokinase nor hexokinase PI showed any effect on this regulatory system. Biochemical analysis in crude extracts also showed altered kinetic properties of hexokinases in the hex1 mutants. The results directly support the hypothesis previously put forward, that one of the hexokinases is not only active as a catalytic, but also as a regulatory protein.
Mol Gen Genet 1980
PMID:Genetic and biochemical evidence for hexokinase PII as a key enzyme involved in carbon catabolite repression in yeast. 699 59

The previously isolated recessive mutant allele hex2-3 of Saccharomyces cerevisiae caused a defect in carbon catabolite repression of maltase, invertase, malate dehydrogenase, and respiration but at the same time led to an extreme sensitivity to maltose (Zimmerman and Scheel, 1977; Entian and Zimmermann, 1980). Addition of maltose to a growing culture of a hex2-3 mutant resulted within 60 to 90 min in an inhibition of growth, glycolysis, and de novo protein synthesis. This was not accompanied by any abnormal levels of glycolysis metabolites or glycolytic enzyme activities. However, inhibitory effects coincided with a dramatic increase in intracellular glucose up to 150 mM relative to cell water as opposed to 2.5 mM in wild-type cells. This abnormal behavior is interpreted as a result of an uncontrolled maltose uptake in hex2 mutants, which in combination with increasing maltase activity results in an accumulation of intracellular glucose. Obviously the amount of available glucose surpassed glycolytic capacity in hex2 mutants. Properties of mutant alleles hex2 and hex1 (see Entian and Zimmermann, 1980) clearly show, that specific gene functions are involved in adapting the rate of sugar uptake into the cell to the actual glycolytic capacity.
Mol Gen Genet 1980
PMID:A defect in carbon catabolite repression associated with uncontrollable and excessive maltose uptake. 700 23

We have previously defined two isozymes of neutral alpha-glucosidase (alpha-D-glucoside glucohydrolase, EC 3.2.1.20) on the basis of differences in electrophoretic mobility and designated these neutral alpha-glucosidase AB and alpha-glucosidase C (Swallow, D.M., Corney, G., Harris, H. and Hirschhorn, R. (1975) Ann. Hum. Gen. 38, 391-406). We now describe differences between the two isozymes with respect to molecular weight, solubility in (NH4)2SO4, glycosylation, isoelectric point and substrate specificities. Neutral alpha-glucosidase C is precipitable in 40-60% (NH4)2SO4, has a molecular weight of 92 000, an isoelectric point of 5.5 and releases glucose from glycogen as well as from low molecular weight artificial and natural substrates containing alpha 1-4 glucosidic linkages. Neutral alpha-glucosidase AB precipitates at 0-40% (NH4)2SO4, binds to concanavalin A, has a molecular weight of greater than 150 000, and does not utilize alpha 1-4 linked glucose substrates larger than a disaccharide. Neutral alpha-glucosidase AB migrates more rapidly to the anode than alpha-glucosidase C when agarose, Cellogel, acrylamide or starch are used as support media. Both isozymes are equally inhibited by Zn2+.
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PMID:Characterization of neutral isozymes of human alpha-glucosidase: differences in substrate specificity, molecular weight and electrophoretic mobility. 701 80

A small percentage of the primary petites isolated from strain 1403-7A-P1, constitutive for maltase synthesis, simultaneously lost the ability to utilize maltose and alpha-methylglucoside. Further studies showed that these primary petites were not stable with respect to maltose utilization. Approximately 30% of the secondary petites when isolated from the primary petites after vegetative growth were found to papillate on maltose plates. Tetrad analysis data revealed that a nuclear gene has reverted in these papillae, which is responsible for suppression of the maltose negative phenotype in primary petites. We have designated this nuclear gene as the PMU1 gene (petite maltose utilizer). The functional form of the PMU1 gene is required in addition to the MAL4 gene for both constitutive maltase synthesis and maltose utilization in cytoplasmic petite cells derived from strain 1403-7A-P1.
Mol Gen Genet 1982
PMID:Suppression of maltose-negative phenotype by a specific nuclear gene (PMU1) in the petite cells of the yeast Saccharomyces cerevisiae. 705 Jun 24

1. We examined the effect of the alpha-glucosidase inhibitor acarbose on urinary albumin excretion (UAE) in streptozotocin diabetic rats. 2. Treatment with acarbose for 8 weeks after induction of diabetes prevented the significant increase in UAE observed in untreated diabetic rats relative to nondiabetic controls. 3. Acarbose significantly reduced integrated glycemia, which correlated with albumin excretion rates, and exerts a salutary effect on diabetic renal dysfunction.
Gen Pharmacol 1995 Oct
PMID:Treatment with acarbose, an alpha-glucosidase inhibitor, reduces increased albumin excretion in streptozotocin-diabetic rats. 759 Jan 31

Maltose utilization in yeast requires the presence of any one of the five unlinked, homologous MAL loci. Transcription of the two structural genes MALT (permease) and MALS (maltase) is induced by maltose and catabolite-repressed by glucose. MAL6T and MAL6S share a common 5' intergenic sequence; deletion studies within this sequence revealed a bi-directionally functioning upstream activation sequence (UASM) consisting of four 11 bp homologous sites. Activation of these sites by the MALR protein results in the coordinate expression of MAL6T and MAL6S. The basal promoter activates MALS expression to a greater extent than MALT and is located in a region that overlaps UASM. Deletion of several subsites within the UASM has an asymmetric effect on MAL gene expression, having a greater affect on MALT than on MALS. Catabolite repression of MAL6T and MAL6S by glucose is controlled at several levels. Using disruption mutants, the positively acting MAL1R protein was also found to play a role in catabolite repression of MAL6T and MAL6S.
Mol Gen Genet 1994 Jun 15
PMID:Shared control of maltose induction and catabolite repression of the MAL structural genes in Saccharomyces. 802 78

The complete nucleotide sequences of four genes and one open reading frame (ORF1) adjacent to the streptokinase gene, skc, from Streptococcus equisimilis H46A were determined. These genes are encoded on the opposite DNA strand to skc and are arranged as follows: dexB-abc-lrp-skc-ORF1-rel. The dexB gene, coding for an alpha-glucosidase (M(r) 61,733), and abc, encoding an ABC transporter (M(r) 42,080), are similar to the dexB and msmK genes, respectively, from the multiple sugar metabolism operon of S. mutans. The lrp gene specifies a leucine-rich protein (M(r) 32,302) that has a leucine-zipper motif at its C-terminus. The function of the Lrp protein is not known but appeared to be detrimental when overexpressed in Escherichia coli. Although lrp appears not to be an essential gene, as judged by plasmid insertion mutagenesis, it is conserved in all streptococcal strains carrying a streptokinase gene. The rel gene showed significant homology to the E. coli relA and spoT genes involved in the stringent response to amino acid deprivation. Multiple alignment of the amino acid sequences of Rel (M(r) 83,913), RelA and SpoT revealed 59.4% homology of the primary structures. Northern hybridization analyses of the genes in the skc region showed skc to be transcribed most abundantly. In addition to transcripts for skc, monocistronic mRNAs were detected for all three genes divergently transcribed from skc. Although there was also some read-through transcription from lrp into abc, and from abc into dexB, the transcription pattern suggests a high degree of transcriptional and functional independence not only of skc but also abc and dexB. Prominent structural features in intergenic regions included a static DNA bending locus located upstream and a putative bidirectional transcription terminator downstream of skc.
Mol Gen Genet 1993 Oct
PMID:Genetic organization of the streptokinase region of the Streptococcus equisimilis H46A chromosome. 823 96


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