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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)

The mechanism of starch degradation by the fungus Trichoderma viride was studied in strain CBS 354.44, which utilizes glucose, starch and dextrins but is unable to assimilate maltose. It was shown that the amylolytic enzyme system is completely extracellular, equally well induced by starch, amylose or amylopectin and that it consists mainly of enzymes of the glucoamylase type which yield glucose as the main product of starch hydrolysis. Small amounts of alpha-amylase are produced also. The enzymes produced in starch cultures degrade starch, amylose and amylopectin equally well. Enzyme synthesis in starch media takes place to a considerable extent after exhaustion of the carbon source when maximum growth has been attained. Low-molecular dextrins are degraded by extracellular enzymes of the glucoamylase type. These enzymes are produced in media containing starch or dextrins. Maltotriose is consumed for only one third leaving maltose in the culture filtrate. Maltose is hardly attacked and hardly induces any amylolytic enzyme activity. No stable alpha-glucosidase appears to be produced.
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PMID:Starch degradation by the mould Trichoderma viride. I. The mechanism of starch degradation. 1 Aug 32

The molecular cloning of an alpha-glucosidase gene isolated from a Candida tsukubaensis (CBS 6389) genomic library in Saccharomyces cervisiae is reported. The cloned gene is contained within a 6.2 kb Sau3A DNA fragment and directs the synthesis and secretion of an amylolytic enzyme into the extracellular medium of the recombinant host, S. cerevisiae. The cloned enzyme was found to have an unusually broad substrate specificity and is capable of hydrolysing alpha-1,2, alpha-1,3, alpha-1,4 and alpha-1,6 linked, as well as aryl and alkyl, D-glucosides. On the basis of its substrate specificity profile, the cloned enzyme was classified as an alpha-glucosidase (E.C. 3.2.1.20). It has a pH optimum in the range 4.2-4.6, a temperature optimum of 58 degrees C and is readily inactivated at pasteurization temperature (60 degrees C). Southern blot analysis failed to reveal any homology between the cloned gene and genomic DNA isolated from other well characterized amylolytic yeasts. A rapid plate-assay, based on the utilization of a chromogenic substrate X-alpha-D-glucoside to detect the expression of the cloned alpha-glucosidase in S. cerevisiae transformants, was developed.
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PMID:Molecular cloning and characterization of a Candida tsukubaensis alpha-glucosidase gene in the yeast Saccharomyces cerevisiae. 193 16

When Saccharomyces cerevisiae CBS 8066 was grown under maltose limitation, two enzymes specific for maltose utilization were present: a maltose carrier, and the maltose-hydrolysing alpha-glucosidase. The role of these two enzymes in the physiology of S. cerevisiae was investigated in a comparative study in which Candida utilis CBS 621 was used as a reference organism. Maltose pulses to a maltose-limited chemostat culture of S. cerevisiae resulted in 'substrate-accelerated death'. This was evident from: (1) enhanced protein release from cells; (2) excretion of glucose into the medium; (3) decreased viability. These effects wee specific with respect to both substrate and organism: pulses of glucose to maltose-limited cultures of S. cerevisiae did not result in cell death, neither did maltose pulses to maltose-limited cultures of C. utilis. The maltose-accelerated death of s. cerevisiae is most likely explained in terms of an uncontrolled uptake of maltose into the cell, resulting in an osmotic burst. Our results also provide evidence that the aerobic alcoholic fermentation that occurs after pulsing sugars to sugar-limited cultures of s. cerevisiae (short-term Crabtree effect) cannot solely be explained in terms of the mechanism of sugar transport. Both glucose and maltose pulses to maltose-limited cultures triggered aerobic alcohol formation. However, glucose transport by S. cerevisiae occurs via facilitated diffusion, whereas maltose entry into this yeast is mediated by a maltose/proton symport system.
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PMID:Substrate-accelerated death of Saccharomyces cerevisiae CBS 8066 under maltose stress. 218 22

The fission yeast Schizosaccharomyces pombe CBS 356 exhibits extracellular maltase activity. This activity may be of commercial interest as it exhibited a low pH optimum (3.5) and a high affinity for maltose (Km of 7.0+/-1.8 mM). N-terminal sequencing of the protein indicates that it is the product of the AGL1 gene. Regulation of this gene occurs via a derepression/repression mechanism. In sugar- or nitrogen-limited chemostat cultures, the specific rate of enzyme production (q(p)) was independent of the nature of the carbon source (i.e. glucose or maltose), but synthesis was partially repressed by high sugar concentrations. Furthermore, q(p) increased linearly with specific growth rate (mu) between 0.04 and 0.10 h(-1). The enzyme is easily mass-produced in aerobic glucose-limited fed-batch cultures, in which the specific growth rate is controlled to prevent alcoholic fermentation. In fed-batch cultures in which biomass concentrations of 83 g L(-1) were attained, the enzyme concentration reached 58,000 Units per liter culture supernatant. Extracellular maltase may be used as a dough additive in order to prevent mechanisms such as maltose-induced glucose efflux and maltose-hypersensitivity that occur in maltose-consuming Saccharomyces cerevisiae.
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PMID:Physiological characterization and fed-batch production of an extracellular maltase of Schizosaccharomyces pombe CBS 356. 1691 11

The filamentous ascomycete Aspergillus niger is well known for its ability to produce a large variety of enzymes for the degradation of plant polysaccharide material. A major carbon and energy source for this soil fungus is starch, which can be degraded by the concerted action of alpha-amylase, glucoamylase and alpha-glucosidase enzymes, members of the glycoside hydrolase (GH) families 13, 15 and 31, respectively. In this study we have combined analysis of the genome sequence of A. niger CBS 513.88 with microarray experiments to identify novel enzymes from these families and to predict their physiological functions. We have identified 17 previously unknown family GH13, 15 and 31 enzymes in the A. niger genome, all of which have orthologues in other aspergilli. Only two of the newly identified enzymes, a putative alpha-glucosidase (AgdB) and an alpha-amylase (AmyC), were predicted to play a role in starch degradation. The expression of the majority of the genes identified was not induced by maltose as carbon source, and not dependent on the presence of AmyR, the transcriptional regulator for starch degrading enzymes. The possible physiological functions of the other predicted family GH13, GH15 and GH31 enzymes, including intracellular enzymes and cell wall associated proteins, in alternative alpha-glucan modifying processes are discussed.
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PMID:Aspergillus niger genome-wide analysis reveals a large number of novel alpha-glucan acting enzymes with unexpected expression profiles. 1832 Feb 28