Starch Degrading and Synthesizing Enzymes: A Discussion of Their Properties and Action Pattern

Greenwood, C. T.; Milne, Elspeth

doi:10.1016/s0096-5332(08)60171-x

Cited by 66 publications

(44 citation statements)

References 287 publications

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“…The K values were plotted using the Arrhenius relationship as shown in Figure 8 which generated an activation energy of 94 kJ/mol. This number agrees with enzyme activation energies typically reported in the literature (Laidler, 1963;Greenwood and Milne, 1968).…”

Section: Enzyme Modelingsupporting

confidence: 91%

Cold enzyme hydrolysis of wheat starch granules

et al. 1998

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Three a-amylase enzymes were used to hydrolyze wheat starch granules suspended in water below the gelatinization temperature. The rates of hydrolysis were determined at various temperatures, pH, enzyme and starch concentrations. Barley amylase was found to be the "best" enzyme when used at pH 4.5,45"C and starch and enzyme concentrations of 30 and 8 mg/mL respectively. It was found that under these conditions, 98% of the starch granules were hydrolyzed in 3 hours, the same amount of time used in the industrial cooking process of soluble starch. Starch particles were observed to be attacked at specific points on the surface and then hydrolyzed from the inside-out. Some granules were hydrolyzed at a very fast rate with a first order rate constant estimated to be 40 h-'; but most granules were hydrolyzed slowly according to the Michaelis-Menten model and the best fit parameters were found to depend on enzyme type, pH and temperature.On a utilise trois enzymes a-amylase pour hydrolyser des granules d'amidon de ble suspendus dans I'eau sous la temperature de gelatinisation.

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Section: Enzyme Modelingsupporting

confidence: 91%

Cold enzyme hydrolysis of wheat starch granules

et al. 1998

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“…4) which is per cent inhibition of a-anomalously low compared to the generally accepted value of (B). Protein used at pH 8.0 about 45,000 D (8). Similar low mol wt have been reported for .…”

Section: Methodssupporting

confidence: 77%

Purification and Characteristics of an Endogenous α-Amylase Inhibitor from Barley Kernels

Weselake¹,

MacGregor²,

Hill³

et al. 1983

Plant Physiol.

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An inhibitor of malted barley (Hordeum vulgare cv Conquest) aamylase II was purified 125-fold from a crude extract of barley kernels by (NH-)42SO4 fractionation, ion exchange chromatography on DEAESephacel, and gel filtration on Bio-Gel P 60. The inhibitor was a protein with an approximate molecular weight of 20,000 daltons and an isoelectric point of 73. The protein was homogeneous, as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Amino acid analysis indicated the presence of about 9 half-cystine residues per mole. The neutral isoelectric point of the inhibitor suggested that some of the apparently acidic residues (glutamic and aspartic) existed in the amide form. The first twenty N-terminal amino acids were sequenced. Some homology appeared to exist between the a-amylase II inhibitor and trypsin inhibitor from barley. Complex formation between a-amylase II and the inhibitor was detected by the appearance of a new molecular weight species after gel filtration on Bio-Gel P 100. Enzyme and inhibitor had to be preincubated for 5 min, prior to assaying for enzyme activity before maximum inhibition was attained. Inhibition increased at higher pH values. At pH 5.5, an approximately 1100 molar excess of inhibitor over a-amylase II produced 40% inhibition, whereas, at pH 8.0, a 1:1 molar ratio of inhibitor to enzyme produced the same degree of inhibition.Frydenberg and Nielsen (7) made an in-depth study of the polymorphism of germinated barley a-amylase using zone electrophoresis on agar gel. They showed that heating of malted barley extracts at 70°C for 15 min resulted in disappearance of some a-amylase bands and enrichment of others. The heat treatment appeared to cause the conversion of a heat labile band of a-amylase to a more stable form having a different electrophoretic mobility. A similar phenomenon was described later by MacGregor and Ballance (14). Using isoelectric focusing, these authors reported the presence ofthree major polymorphic groups of a-amylase, designated a-amylases I, II, and III, in extracts of malted barley. Quantitative determination ofthese groups before and after a 15-min heat treatment at 70°C showed almost com- (22,23) and maize (1) kernels. Purothionins have been implicated also as inhibitors of wheat a-amylase (9). However, most research on a-amylase inhibitors has been restricted to a family of albumins isolated from wheat kernels (3). These albumins do not have inhibitory activity against cereal aamylases.The current investigation describes the purification, amino acid composition, and some physicochemical properties of the factor that binds specifically to, and inhibits a-amylase II, converting it to a-amylase III. Some parameters affecting the enzyme-inhibitor interaction will be discussed. MATERIALS AND METHODSPurification of Inhibitor. The inhibitor was purified from barley (Hordeum distichum cv Klages) kernels, essentially as described by Weselake et al. (24). Flour prepared from dehusked barley kernels (85 g) was extracted for 1 h (4C) with 420 ...

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“…This sequence of formation of the products from maltotriose favours the multi-chain mechanism (Greenwood & Milne, 1968) as the predominant mechanism operative for the hydrolysis of maltotriose by T. lanuginosus glucoamylase.…”

Section: Action Patterns Ofglucoamylasementioning

confidence: 80%

Purification and characterization of a thermostable glucoamylase from the thermophilic fungus Thermomyces lanuginosus

Rao¹,

Sastri²,

Rao³

1981

Biochemical Journal

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Glucoamylase (1,4-alpha-D-glucan glucohydrolase, EC 3.2.1.3) was purified from the culture filtrates of the thermophilic fungus Thermomyces lanuginosus and was established to be homogeneous by a number of criteria. The enzyme was a glycoprotein with an average molecular weight of about 57 000 and a carbohydrate content of 10-12%. The enzyme hydrolysed successive glucose residues from the non-reducing ends of the starch molecule. It did not exhibit any glucosyltransferase activity. The enzyme appeared to hydrolyse maltotriose by the multi-chain mechanism. The enzyme was unable to hydrolyse 1,6-alpha-D-glucosidic linkages of isomaltose and dextran. It was optimally active at 70 degrees C. The enzyme exhibited increase in the Vmax. and decreased in Km values with increasing chain length of the substrate molecule. The enzyme was inhibited by the substrate analogue D-glucono-delta-lactone in a non-competitive manner. The enzyme inhibited remarkable resistance towards chemical and thermal denaturation.

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Starch Degrading and Synthesizing Enzymes: A Discussion of Their Properties and Action Pattern

Cited by 66 publications

References 287 publications

Cold enzyme hydrolysis of wheat starch granules

Cold enzyme hydrolysis of wheat starch granules

Purification and Characteristics of an Endogenous α-Amylase Inhibitor from Barley Kernels

Purification and characterization of a thermostable glucoamylase from the thermophilic fungus Thermomyces lanuginosus

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