Amylase

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Birte Svensson - One of the best experts on this subject based on the ideXlab platform.

  • α-Amylase: an enzyme specificity found in various families of glycoside hydrolases
    Cellular and Molecular Life Sciences, 2014
    Co-Authors: Stefan Janecek, Birte Svensson, E. Ann Macgregor
    Abstract:

    α-Amylase (EC 3.2.1.1) represents the best known amylolytic enzyme. It catalyzes the hydrolysis of α-1,4-glucosidic bonds in starch and related α-glucans. In general, the α-Amylase is an enzyme with a broad substrate preference and product specificity. In the sequence-based classification system of all carbohydrate-active enzymes, it is one of the most frequently occurring glycoside hydrolases (GH). α-Amylase is the main representative of family GH13, but it is probably also present in the families GH57 and GH119, and possibly even in GH126. Family GH13, known generally as the main α-Amylase family, forms clan GH-H together with families GH70 and GH77 that, however, contain no α-Amylase. Within the family GH13, the α-Amylase specificity is currently present in several subfamilies, such as GH13_1, 5, 6, 7, 15, 24, 27, 28, 36, 37, and, possibly in a few more that are not yet defined. The α-Amylases classified in family GH13 employ a reaction mechanism giving retention of configuration, share 4–7 conserved sequence regions (CSRs) and catalytic machinery, and adopt the (β/α)_8-barrel catalytic domain. Although the family GH57 α-Amylases also employ the retaining reaction mechanism, they possess their own five CSRs and catalytic machinery, and adopt a (β/α)_7-barrel fold. These family GH57 attributes are likely to be characteristic of α-Amylases from the family GH119, too. With regard to family GH126, confirmation of the unambiguous presence of the α-Amylase specificity may need more biochemical investigation because of an obvious, but unexpected, homology with inverting β-glucan-active hydrolases.

  • structure specificity and function of cyclomaltodextrinase a multispecific enzyme of the α Amylase family
    Biochimica et Biophysica Acta, 2000
    Co-Authors: Kwan-hwa Park, Taekyou Cheong, Byungha Oh, Birte Svensson
    Abstract:

    Abstract Cyclomaltodextrinase (CDase, EC 3.2.1.54), maltogenic Amylase (EC 3.2.1.133), and neopullulanase (EC 3.2.1.135) are reported to be capable of hydrolyzing all or two of the following three types of substrates: cyclomaltodextrins (CDs); pullulan; and starch. These enzymes hydrolyze CDs and starch to maltose and pullulan to panose by cleavage of α-1,4 glycosidic bonds whereas α-Amylases essentially lack activity on CDs and pullulan. They also catalyze transglycosylation of oligosaccharides to the C3-, C4- or C6-hydroxyl groups of various acceptor sugar molecules. The present review surveys the biochemical, enzymatic, and structural properties of three types of such enzymes as defined based on the substrate specificity toward the CDs: type I, cyclomaltodextrinase and maltogenic Amylase that hydrolyze CDs much faster than pullulan and starch; type II, Thermoactinomyces vulgaris Amylase II (TVA II) that hydrolyzes CDs much less efficiently than pullulan; and type III, neopullulanase that hydrolyzes pullulan efficiently, but remains to be reported to hydrolyze CDs. These three types of enzymes exhibit 40–60% amino acid sequence identity. They occur in the cytoplasm of bacteria and have molecular masses from 62 to 90 kDa which are slightly larger than those of most α-Amylases. Multiple amino acid sequence alignment and crystal structures of maltogenic Amylase and TVA II reveal the presence of an N-terminal extension of approximately 130 residues not found in α-Amylases. This unique N-terminal domain as seen in the crystal structures apparently contributes to the active site structure leading to the distinct substrate specificity through a dimer formation. In aqueous solution, most of these enzymes show a monomer–dimer equilibrium. The present review discusses the multiple specificity in the light of the oligomerization and the molecular structures arriving at a clarified enzyme classification. Finally, a physiological role of the enzymes is proposed.

  • Protein engineering in the α-Amylase family: catalytic mechanism, substrate specificity, and stability
    Plant Molecular Biology, 1994
    Co-Authors: Birte Svensson
    Abstract:

    Most starch hydrolases and related enzymes belong to the α-Amylase family which contains a characteristic catalytic (β/α)_8-barrel domain. Currently known primary structures that have sequence similarities represent 18 different specificities, including starch branching enzyme. Crystal structures have been reported in three of these enzyme classes: the α-Amylases, the cyclodextrin glucanotransferases, and the oligo-1,6-glucosidases. Throughout the α-Amylase family, only eight amino acid residues are invariant, seven at the active site and a glycine in a short turn. However, comparison of three-dimensional models with a multiple sequence alignment suggests that the diversity in specificity arises by variation in substrate binding at the β→α loops. Designed mutations thus have enhanced transferase activity and altered the oligosaccharide product patterns of α-Amylases, changed the distribution of α-, β- and γ-cyclodextrin production by cyclodextrin glucanotransferases, and shifted the relative α-1,4:α-1,6 dual-bond specificity of neopullulanase. Barley α-Amylase isozyme hybrids and Bacillus α-Amylases demonstrate the impact of a small domain B protruding from the (β/α)_8-scaffold on the function and stability. Prospects for rational engineering in this family include important members of plant origin, such as α-Amylase, starch branching and debranching enzymes, and amylomaltase.

  • protein engineering in the alpha Amylase family catalytic mechanism substrate specificity and stability
    Plant Molecular Biology, 1994
    Co-Authors: Birte Svensson
    Abstract:

    Most starch hydrolases and related enzymes belong to the α-Amylase family which contains a characteristic catalytic (β/α)8-barrel domain. Currently known primary structures that have sequence similarities represent 18 different specificities, including starch branching enzyme. Crystal structures have been reported in three of these enzyme classes: the α-Amylases, the cyclodextrin glucanotransferases, and the oligo-1,6-glucosidases. Throughout the α-Amylase family, only eight amino acid residues are invariant, seven at the active site and a glycine in a short turn. However, comparison of three-dimensional models with a multiple sequence alignment suggests that the diversity in specificity arises by variation in substrate binding at the β→α loops. Designed mutations thus have enhanced transferase activity and altered the oligosaccharide product patterns of α-Amylases, changed the distribution of α-, β- and γ-cyclodextrin production by cyclodextrin glucanotransferases, and shifted the relative α-1,4:α-1,6 dual-bond specificity of neopullulanase. Barley α-Amylase isozyme hybrids and Bacillus α-Amylases demonstrate the impact of a small domain B protruding from the (β/α)8-scaffold on the function and stability. Prospects for rational engineering in this family include important members of plant origin, such as α-Amylase, starch branching and debranching enzymes, and amylomaltase.

Michael J Gidley - One of the best experts on this subject based on the ideXlab platform.

  • effects of processing high amylose maize starches under controlled conditions on structural organisation and Amylase digestibility
    Carbohydrate Polymers, 2009
    Co-Authors: Aung K Htoon, Ashok K Shrestha, Bernadine M Flanagan, Amparo Lopezrubio, Anthony R Bird, Elliot P Gilbert, Michael J Gidley
    Abstract:

    The Amylase digestibility of high-amylose maize starches has been compared before and after thermomechanical processing. Starches were analysed for enzyme-resistant starch yield, apparent amylose content, crystallinity (X-ray diffraction), and molecular order (NMR and FTIR), both before and after treatment with a-Amylase. All samples had significant (>10%) enzyme-resistant starch levels irrespective of the type and extent of thermal or enzymic processing. Molecular or crystalline order was not a pre-requisite for enzyme resistance. Near-amorphous forms of high amylose maize starches are likely to undergo recrystallisation during the enzyme-digestion process. The mechanism of enzyme resistance of granular high-amylose starches is found to be qualitatively different to that for processed high-amylose starches. For all samples, measured levels of enzyme resistance are due to the interruption of a slow digestion process, rather than the presence of completely indigestible material. 2008 Elsevier Ltd. All rights reserved.

Ashok K Shrestha - One of the best experts on this subject based on the ideXlab platform.

  • effects of processing high amylose maize starches under controlled conditions on structural organisation and Amylase digestibility
    Carbohydrate Polymers, 2009
    Co-Authors: Aung K Htoon, Ashok K Shrestha, Bernadine M Flanagan, Amparo Lopezrubio, Anthony R Bird, Elliot P Gilbert, Michael J Gidley
    Abstract:

    The Amylase digestibility of high-amylose maize starches has been compared before and after thermomechanical processing. Starches were analysed for enzyme-resistant starch yield, apparent amylose content, crystallinity (X-ray diffraction), and molecular order (NMR and FTIR), both before and after treatment with a-Amylase. All samples had significant (>10%) enzyme-resistant starch levels irrespective of the type and extent of thermal or enzymic processing. Molecular or crystalline order was not a pre-requisite for enzyme resistance. Near-amorphous forms of high amylose maize starches are likely to undergo recrystallisation during the enzyme-digestion process. The mechanism of enzyme resistance of granular high-amylose starches is found to be qualitatively different to that for processed high-amylose starches. For all samples, measured levels of enzyme resistance are due to the interruption of a slow digestion process, rather than the presence of completely indigestible material. 2008 Elsevier Ltd. All rights reserved.

Toshiaki Kudo - One of the best experts on this subject based on the ideXlab platform.

  • purification characterization and nucleotide sequence of an intracellular maltotriose producing alpha Amylase from streptococcus bovis 148
    Applied and Environmental Microbiology, 1997
    Co-Authors: Eiichi Satoh, Toshiaki Kudo, Tai Uchimura, Kazuo Komagata
    Abstract:

    An intracellular alpha-Amylase from Streptococcus bovis 148 was purified and characterized. The enzyme was induced by maltose and soluble starch and produced about 80% maltotriose from soluble starch. Maltopentaose was hydrolyzed to maltotriose and maltose and maltohexaose was hydrolyzed mainly to maltotriose by the enzyme. Maltotetraose, maltotriose, and maltose were not hydrolyzed. This intracellular enzyme was considered to be a maltotriose-producing enzyme. The enzymatic characteristics and hydrolysis product from soluble starch were different from those of the extracellular raw-starch-hydrolyzing alpha-Amylase of strain 148. The deduced amino acid sequence of the intracellular alpha-Amylase was similar to the sequences of the mature forms of extracellular liquefying alpha-Amylases from Bacillus strains, although the intracellular alpha-Amylase did not contain a signal peptide. No homology between the intracellular and extracellular alpha-Amylases of S. bovis 148 was observed.

  • purification and properties of extracellular Amylase from the hyperthermophilic archaeon thermococcus profundus dt5432
    Applied and Environmental Microbiology, 1995
    Co-Authors: Young Chul Chung, Tetsuo Kobayashi, H Kanai, T Akiba, Toshiaki Kudo
    Abstract:

    A hyperthermophilic archaeon, Thermococcus profundus DT5432, produced extracellular thermostable Amylases. One of the Amylases (Amylase S) was purified to homogeneity by ammonium sulfate precipitation, DEAE-Toyopearl chromatography, and gel filtration on Superdex 200HR. The molecular weight of the enzyme was estimated to be 42,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The Amylase exhibited maximal activity at pH 5.5 to 6.0 and was stable in the range of pH 5.9 to 9.8. The optimum temperature for the activity was 80(deg)C. Half-life of the enzyme was 3 h at 80(deg)C and 15 min at 90(deg)C. Thermostability of the enzyme was enhanced in the presence of 5 mM Ca(sup2+) or 0.5% soluble starch at temperatures above 80(deg)C. The enzyme activity was inhibited in the presence of 5 mM iodoacetic acid or 1 mM N-bromosuccinimide, suggesting that cysteine and tryptophan residues play an important role in the catalytic action. The Amylase hydrolyzed soluble starch, amylose, amylopectin, and glycogen to produce maltose and maltotriose of (alpha)-configuration as the main products. Smaller amounts of larger maltooligosaccharides were also produced with a trace amount of glucose. Pullulan; (alpha)-, (beta)-, and (gamma)-cyclodextrins; maltose; and maltotriose were not hydrolyzed.

Daniel J Rigden - One of the best experts on this subject based on the ideXlab platform.

  • Plant alpha-Amylase inhibitors and their interaction with insect alpha-Amylases.
    FEBS Journal, 2002
    Co-Authors: Octavio L Franco, Daniel J Rigden, Francislete R Melo, Maria Fatima Grossi-de-sa
    Abstract:

    : Insect pests and pathogens (fungi, bacteria and viruses) are responsible for severe crop losses. Insects feed directly on the plant tissues, while the pathogens lead to damage or death of the plant. Plants have evolved a certain degree of resistance through the production of defence compounds, which may be aproteic, e.g. antibiotics, alkaloids, terpenes, cyanogenic glucosides or proteic, e.g. chitinases, beta-1,3-glucanases, lectins, arcelins, vicilins, systemins and enzyme inhibitors. The enzyme inhibitors impede digestion through their action on insect gut digestive alpha-Amylases and proteinases, which play a key role in the digestion of plant starch and proteins. The natural defences of crop plants may be improved through the use of transgenic technology. Current research in the area focuses particularly on weevils as these are highly dependent on starch for their energy supply. Six different alpha-Amylase inhibitor classes, lectin-like, knottin-like, cereal-type, Kunitz-like, gamma-purothionin-like and thaumatin-like could be used in pest control. These classes of inhibitors show remarkable structural variety leading to different modes of inhibition and different specificity profiles against diverse alpha-Amylases. Specificity of inhibition is an important issue as the introduced inhibitor must not adversely affect the plant's own alpha-Amylases, nor the nutritional value of the crop. Of particular interest are some bifunctional inhibitors with additional favourable properties, such as proteinase inhibitory activity or chitinase activity. The area has benefited from the recent determination of many structures of alpha-Amylases, inhibitors and complexes. These structures highlight the remarkable variety in structural modes of alpha-Amylase inhibition. The continuing discovery of new classes of alpha-Amylase inhibitor ensures that exciting discoveries remain to be made. In this review, we summarize existing knowledge of insect alpha-Amylases, plant alpha-Amylase inhibitors and their interaction. Positive results recently obtained for transgenic plants and future prospects in the area are reviewed.

  • plant α Amylase inhibitors and their interaction with insect α Amylases structure function and potential for crop protection
    FEBS Journal, 2002
    Co-Authors: Octavio L Franco, Daniel J Rigden, Francislete R Melo, Maria Fatima Grossidesa
    Abstract:

    Insect pests and pathogens (fungi, bacteria and viruses) are responsible for severe crop losses. Insects feed directly on the plant tissues, while the pathogens lead to damage or death of the plant. Plants have evolved a certain degree of resistance through the production of defence compounds, which may be aproteic, e.g. antibiotics, alkaloids, terpenes, cyanogenic glucosides or proteic, e.g. chitinases, β-1,3-glucanases, lectins, arcelins, vicilins, systemins and enzyme inhibitors. The enzyme inhibitors impede digestion through their action on insect gut digestive α-Amylases and proteinases, which play a key role in the digestion of plant starch and proteins. The natural defences of crop plants may be improved through the use of transgenic technology. Current research in the area focuses particularly on weevils as these are highly dependent on starch for their energy supply. Six different α-Amylase inhibitor classes, lectin-like, knottin-like, cereal-type, Kunitz-like, γ-purothionin-like and thaumatin-like could be used in pest control. These classes of inhibitors show remarkable structural variety leading to different modes of inhibition and different specificity profiles against diverse α-Amylases. Specificity of inhibition is an important issue as the introduced inhibitor must not adversely affect the plant's own α-Amylases, nor the nutritional value of the crop. Of particular interest are some bifunctional inhibitors with additional favourable properties, such as proteinase inhibitory activity or chitinase activity. The area has benefited from the recent determination of many structures of α-Amylases, inhibitors and complexes. These structures highlight the remarkable variety in structural modes of α-Amylase inhibition. The continuing discovery of new classes of α-Amylase inhibitor ensures that exciting discoveries remain to be made. In this review, we summarize existing knowledge of insect α-Amylases, plant α-Amylase inhibitors and their interaction. Positive results recently obtained for transgenic plants and future prospects in the area are reviewed.

  • purification biochemical characterisation and partial primary structure of a new α Amylase inhibitor from secale cereale rye
    The International Journal of Biochemistry & Cell Biology, 2000
    Co-Authors: Jorge Iulek, Octavio L Franco, Daniel J Rigden, Marcio Luis Andrade E Silva, Christiane Trevisan Slivinski, Carlos Bloch
    Abstract:

    Plant α-Amylase inhibitors show great potential as tools to engineer resistance of crop plants against pests. Their possible use is, however, complicated by the observed variations in specificity of enzyme inhibition, even within closely related families of inhibitors. Better understanding of this specificity depends on modelling studies based on ample structural and biochemical information. A new member of the α-Amylase inhibitor family of cereal endosperm has been purified from rye using two ionic exchange chromatography steps. It has been characterised by mass spectrometry, inhibition assays and N-terminal protein sequencing. The results show that the inhibitor has a monomer molecular mass of 13 756 Da, is capable of dimerisation and is probably glycosylated. The inhibitor has high homology with the bifunctional α-Amylase/trypsin inhibitors from barley and wheat, but much poorer homology with other known inhibitors from rye. Despite the homology with bifunctional inhibitors, this inhibitor does not show activity against mammalian or insect trypsin, although activity against porcine pancreatic, human salivary, Acanthoscelides obtectus and Zabrotes subfasciatus α-Amylases was observed. The inhibitor is more effective against insect α-Amylases than against mammalian enzymes. It is concluded that rye contains a homologue of the bifunctional α-Amylase/trypsin inhibitor family without activity against trypsins. The necessity of exercising caution in assigning function based on sequence comparison is emphasised.