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

We have physically and functionally identified three genes at the MAL6 locus of Saccharomyces carlsbergensis. Using multicopy yeast plasmid vectors, we have subcloned various segments of the entire MAL6 locus. The functional characterization of the MAL6 subcloned regions was determined by (1) analyzing biochemically the levels of MAL-encoded proteins (maltase [alpha-D-glucosidase, E.C. 3.2.1.20] and maltose transport protein) in cells transformed with various MAL6 subclones, and (2) testing the ability of the subclones to complement the maltose fermentation defects of well characterized Mal- mutants in the highly homologous MAL1 locus. The physical homology between MAL6 and MAL1 is in part demonstrated by the gene disruption of MAL1 using subcloned MAL6 DNA sequences. The results demonstrate that the MAL6 locus is a complex of at least three genes: MAL6R, MAL6T and MAL6S. These genes specify, respectively, a regulatory function, a maltose transport activity (presumably the maltose permease) and the structural gene for maltase. The functional organization of the MAL6 locus is thus identical to that which we had previously determined by mutational analysis for the MAL1 locus.
 ...
PMID:Organization of the MAL loci of Saccharomyces. Physical identification and functional characterization of three genes at the MAL6 locus. 299 4

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)
 ...
PMID:Mutational analysis of the MAL1 locus of Saccharomyces: identification and functional characterization of three genes. 638 96

We report the DNA sequence of a segment located on the right arm of chromosome II from Saccharomyces cerevisiae S288C near the subtelomeric sequences. The sequence was determined using a random cloning strategy followed by an oligonucleotide-directed sequencing. The segment contains four non-overlapping open reading frames (ORFs) YBR297w, YBR298c, YBR299w and YBR301c, and two overlapping ones (YBR300c and YBR300w). Three of them--YBR297w, YBR298c and YBR299w--are the MAL3R (transcriptional regulatory protein), MAL3T (maltose permease) and MAL3S (maltase) genes of the MAL3 locus previously localized. The three other ORFs are unidentified. Another MAL locus (MALl) has been localized on chromosome VII. The Mal- phenotype of strain S288c cannot be explained by telomeric silencing.
 ...
PMID:Sequence of a 9.8 kb segment of yeast chromosome II including the three genes of the MAL3 locus and three unidentified open reading frames. 748 39

A gene coding for a putative alpha-glucosidase has been identified in the open reading frame yvdL (now termed malL), which was sequenced as part of the Bacillus subtilis genome project. The enzyme was overproduced in Escherichia coli and purified. Further analyses indicate that MalL is a specific oligo-1,4-1,6-alpha-glucosidase (sucrase-maltase-isomaltase). MalL expression in B. subtilis requires maltose induction and is subject to carbon catabolite repression by glucose and fructose. Insertional mutagenesis of malL resulted in a complete inactivation of the maltose-inducible alpha-glucosidase activity in crude protein extracts and a Mal- phenotype.
 ...
PMID:Identification and enzymatic characterization of the maltose-inducible alpha-glucosidase MalL (sucrase-isomaltase-maltase) of Bacillus subtilis. 957 15

Induction of the Saccharomyces MAL structural genes encoding maltose permease and maltase requires the MAL activator, a DNA-binding transcription activator. Genetic analysis of MAL activator mutations suggested that protein folding and stability play an important role in MAL activator regulation and led us to explore the role of the Hsp90 molecular chaperone complex in the regulation of the MAL activator. Strains carrying mutations in genes encoding components of the Hsp90 chaperone complex, hsc82 Delta hsp82-T101I and hsc82 Delta cpr7 Delta, are defective for maltase induction and exhibit significantly reduced growth rates on media containing a limiting concentration of maltose (0.05%). This growth defect is suppressed by providing maltose in excess. Using epitope-tagged alleles of the MAL63 MAL activator, we showed that Mal63p levels are drastically reduced following depletion of cellular Hsp90. Overexpression ( approximately 3-fold) of Mal63p in the hsc82 Delta hsp82-T101I and hsc82 Delta cpr7 Delta strains suppresses their Mal- growth phenotype, suggesting that Mal63p levels are limiting for maltose utilization in strains with abrogated Hsp90 activity. Consistent with this, the half-life of Mal63p is significantly shorter in the hsc82 Delta cpr7 Delta strain (reduced about 6-fold) and modestly affected in the Hsp90-ts strain (reduced about 2-fold). Most importantly, triple hemagglutinin-tagged Mal63p protein is found in association with Hsp90 as demonstrated by co-immunoprecipitation. Taken together, these results identify the inducible MAL activator as a client protein of the Hsp90 molecular chaperone complex and point to a critical role for chaperone function in alternate carbon source utilization in Saccharomyces cerevisiae.
 ...
PMID:The Hsp90 molecular chaperone complex regulates maltose induction and stability of the Saccharomyces MAL gene transcription activator Mal63p. 1450 Jul 8

Yeast strains carrying a functional MAL locus are inducible for the co-ordinate synthesis of both maltase and maltose permease when grown in the presence of maltose. Whether the maltose permease is encoded by a gene at the MAL loci has remained unclear due to the lack of mutants in this function. To isolate mutants defective in maltose transport, a positive selection strategy was employed in which a number of Mal(-) mutants were obtained. Among these one Mal- mutant was isolated which had normal levels of wild-type maltase in cell free extracts. This isolate, designated MGT1, has a defect in maltose transport (malT1), detected by its markedly lower uptake of [(14)C]maltose, and by its growth on media containing 10% but not 2% maltose. Since the Km of maltose uptake is altered 10-fold in this mutant and the Vmax remains unchanged, it is suggested that the mutation alters the structure of the maltose permease involved in transport of the disaccharide into the cell rather than its regulation.A genetic analysis of the malT1 mutation shows that it is in a gene allelic to one at the MAL1 locus. Transformation of this mutant to the Mal(+) phenotype using a chimeric yeast/E. coli shuttle plasmid containing a subcloned fragment of the MAL6 locus suggests that the presence of a functional analogue of the gene encoding the maltose transport function is an integral part of the MAL6 locus as well.
...
PMID:Isolation and characterization of a maltose transport mutant in the yeast Saccharomyces cerevisiae. 2417 78