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)

To utilise maltose as a carbon source Saccharomyces cerevisiae needs one or more functional MAL loci that contain the MALx1 gene encoding maltose permease, MALx2 encoding maltase, and MALx3 encoding a transcriptional activator. Maltose causes a rapid MALx3-dependent induction of MAL gene transcription, and glucose represses this activation via Mig1p. A MALx3 gene conveying high MAL gene expression in the absence of maltose in a malx3 laboratory mutant strain has been isolated from baker's yeast. The construction of hybrid genes between the isolated gene and a highly regulated MALx3 gene showed that constitutivity was the result of multiple amino-acid alterations throughout the structural gene. The combined effect of these amino-acid alterations was shown to be stronger than the sum of their individual effects on constitutivity. Analysis in glucose-repressed conditions confirmed that increased MALx3 transcript levels increased the glucose insensitivity of MAL gene expression but did not affect constitutivity. Analysis of four mutations between aa 343 and 375, lying within a proposed negative regulatory domain, showed that the single mutation of Leu343Phe increased the glucose insensitivity of MAL gene expression by 30-fold. These results demonstrate that not only Mig1p modulation of MALx3 expression, but also the MALx3 protein structure, is involved in the glucose-insensitive expression of the MAL genes.
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PMID:Leu343Phe substitution in the Malx3 protein of Saccharomyces cerevisiae increases the constitutivity and glucose insensitivity of MAL gene expression. 1036 55

A gene, designated amyR, coding for a transcriptional activator involved in amylolytic gene expression has been cloned from Aspergillus oryzae by screening for a clone that enabled to reverse the reduced expression of the alpha-amylase gene (amyB) promoter. amyR encodes 604 amino acid residues of a putative DNA-binding protein carrying a zinc binuclear cluster motif (Zn(II)2Cys6) belonging to the GAL4 family of transcription factors. The amyR gene disruptants showed a significant restricted growth on starch medium and produced little of the amylolytic enzymes including alpha-amylase and glucoamylase compared with a non-disruptant, indicating that amyR is a transcriptional activator gene involved in starch/maltose-induced efficient expression of the amylolytic genes in A. oryzae. In addition, sequencing analysis found that amyR, agdA (encoding alpha-glucosidase), and amyA (encoding alpha-amylase), are clustered on a 12-kb DNA fragment of the largest chromosome in A. oryzae, and that amyR is about 1.5 kb upstream of agdA and transcribed in the opposite direction. Furthermore, transcriptional analysis revealed that the amyR gene was expressed in the presence of glucose comparable to the level in the presence of maltose, while the amylolytic genes were transcribed at high levels only in the presence of maltose.
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PMID:Molecular cloning and characterization of a transcriptional activator gene, amyR, involved in the amylolytic gene expression in Aspergillus oryzae. 1083 Apr 98

The maltose transporter gene is situated at the MAL locus, which consists of genes for a transporter, maltase, and transcriptional activator. Five unlinked MAL loci (MAL1, MAL2, MAL3, MAL4, and MAL6) constitute a gene family in Saccharomyces cerevisiae. The expression of the maltose transporter is induced by maltose and repressed by glucose. The activity of the maltose transporter is also regulated post-translationally; Mal61p is rapidly internalized from the plasma membrane and degraded by ubiquitin-mediated proteolysis in the presence of glucose. We found that S. cerevisiae strain ATCC20598 harboring MAL21 could grow in maltose supplemented with a non- assimilable glucose analogue, 2-deoxyglucose, whereas strain ATCC96955 harboring MAL61 and strain CB11 with MAL31 and AGT1 could not. These observations implied a Mal21p-specific resistance against glucose-induced degradation. Mal21p found in ATCC20598 has 10 amino acids, including Gly-46 and His-50, that are inconsistent with the corresponding residues in Mal61p. The half-life of Mal21p for glucose-induced degradation was 118 min when expressed using the constitutive TPI1 promoter, which was significantly longer than that of Mal61p (25 min). Studies with mutant cells that are defective in endocytosis or the ubiquitination process indicated that Mal21p was less ubiquitinated than Mal61p, suggesting that Mal21p remains on the plasma membrane because of poor susceptibility to ubiquitination. Mutational studies revealed that both residues Gly-46 and His-50 in Mal21p are essential for the full resistance of maltose transporters against glucose-induced degradation.
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PMID:Gly-46 and His-50 of yeast maltose transporter Mal21p are essential for its resistance against glucose-induced degradation. 1935 40

Starch and maltooligosaccharides such as maltose and maltotriose induce the production of amylolytic enzymes including alpha-amylase in Aspergillus oryzae. A transcriptional activator gene amyR, required for maltose induction of amylolytic enzymes, has been cloned and characterized. The amyR gene deletion mutant showed significantly poor growth on starch medium but normal growth on maltose medium. This indicated the existence of another maltose-utilizing system, whose expression might not be controlled by amyR. We have identified a gene cluster homologous to the MAL cluster of Saccharomyces cerevisiae in the A. oryzae genome. The cluster consists of a MAL61 homolog (designated malP), a MAL62 homolog (designated malT), and a MAL63 homolog (designated malR). Overexpression of malT in A. oryzae resulted in a significant increase in intracellular alpha-glucosidase activity, and that of malP allowed S. cerevisiaemal61Delta to grow on maltose. The expression of both malP and malT genes was highly up-regulated in the presence of maltose, but malR expressed constitutively irrespective of carbon sources. Disruption of malR resulted in the loss of malP and malT expression and thus in restricted growth on maltose medium. In addition, a malP disruptant showed a significantly reduced expression of malT and malR and exhibited a growth defect on maltose similar to the malR disruptant. These results suggest that the MAL cluster of A. oryzae is responsible for the assimilation of maltose in A. oryzae.
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PMID:Characterization and expression analysis of a maltose-utilizing (MAL) cluster in Aspergillus oryzae. 1985 Jan 46

HAP4 encodes a transcriptional activator of respiration-related genes and so, redirection from fermentation to respiration flux should give rise to an increase in biomass production in Saccharomyces cerevisiae transformants that overexpress HAP4. With this aim, three bakers' yeasts, that is, V1 used for lean doughs, its 2-deoxy-D-glucose resistant derivative DOG21, and V3 employed for sweet doughs, were transformed with integrative cassettes that carried HAP4 gene under the control of constitutive promoter pTEF2; in addition VTH, DTH and 3TH transformants were selected and characterized. Transformants showed increased expression of HAP4 and respiration-related genes such as QCR7 and QCR8 with regard to parental, and similar expression of SUC2 and MAL12; these genes are relevant in bakers' industry. Invertase (Suc2p) and maltase (Mal12p) activities, growth and sugar consumption rates in laboratory (YPD) or industrial media (MAB) were also comparable in bakers' strains and their transformants, but VTH, DTH and 3TH increased their final biomass production by 9.5, 5.0 and 5.0% respectively as compared to their parentals in MAB. Furthermore, V1 and its transformant VTH had comparable capacity to ferment lean doughs (volume increase rate and final volume) while V3 and its transformant 3TH fermented sweet doughs in a similar manner. Therefore transformants possessed increased biomass yield and appropriate characteristics to be employed in bakers' industry because they lacked drug resistant markers and bacterial DNA, and were genetically stable.
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PMID:Increased biomass production of industrial bakers' yeasts by overexpression of Hap4 gene. 2083 86