Beta-amylase in germinating millet seeds

Selenite affected photosynthesis of Oryza sativa L. exposed to antimonite: Electron transfer, carbon fixation, pigment synthesis via a combined analysis of physiology and transcriptome

Selenium (Se) is a microelement that can counteract (a)biotic stresses in plants. Excess antimony (Sb) will inhibit plant photosynthesis, which can be alleviated by appropriate doses of Se but the associated mechanisms at the molecular levels have not been fully explored. Here, a rice variety (Yongyou 9) was exposed to selenite [Se(IV), 0.2 and 0.8 mg L-1] alone or combined with antimonite [Sb(III), 5 and 10 mg L-1]. When compared to the 10 mg L-1 Sb treatment alone, addition of Se in a dose-dependent manner 1) reduced the heat dissipation efficiency resulting from the inhibited donors, Sb concentrations in shoots and roots, leaf concentrations of fructose, H2O2 and O2•-; 2) enhanced heat dissipation efficiency resulting from the inhibited accepters value, concentrations of Chl a, sucrose and starch, and the enzyme activity of adenosine diphosphate glucose pyrophosphorylase, sucrose phosphate synthase, and sucrose synthase; but 3) did not alter gas exchange parameters, concentrations of Chl b and total Chl, enzyme activity of soluble acid invertase, and values of maximum P700 signal, photochemical efficiency of PSI and electron transport rate of PSI. Se alleviated the damage caused by Sb to the oxygen-evolving complex and promoted the transfer of electrons from QA to QB. When compared to the 10 mg L-1 Sb treatment alone, addition of Se 1) up-regulated genes correlated to synthesis pathways of Chl, carotenoid, sucrose and glucose; 2) disturbed signal transduction pathway of abscisic acid; and 3) upregulated gene expression correlated to photosynthetic complexes (OsFd1, OsFER1 and OsFER2).

Biochemical Properties of β-Amylase from Red Algae and Improvement of Its Thermostability through Immobilization

β-Amylase hydrolyzes polysaccharides, such as starch, into maltose. It is used as an industrial enzyme in the production of food and pharmaceuticals. The eukaryotic red alga Cyanidioschyzon merolae is a unicellular alga that grows at an optimum pH of 2.0-3.0 and an optimum temperature of 40-50 °C. By focusing on the thermostability and acid resistance of the proteins of C. merolae, we investigated the properties of β-amylase from C. merolae (hereafter CmBAM) and explored the possibility of using CmBAM as an industrial enzyme. CmBAM showed the highest activity at 47 °C and pH 6.0. CmBAM had a relatively higher specificity for amylose as a substrate than for starch. Immobilization of CmBAM on a silica gel carrier improved storage stability and thermostability, allowing the enzyme to be reused. The optimum temperature and pH of CmBAM were comparable to those of existing β-amylases from barley and wheat. C. merolae does not use amylose, but CmBAM has a substrate specificity for both amylose and amylopectin but not for glycogen. Among the several β-amylases reported, CmBAM was unique, with a higher specificity for amylose than for starch. The high specificity of CmBAM for amylose suggests that isoamylase and pullulanase, which cleave the α-1,6 bonds of starch, may act together in vivo. Compared with several reported immobilized plant-derived β-amylases, immobilized CmBAM was comparable to β-amylase, with the highest reusability and the third-highest storage stability at 30 days of storage. In addition, immobilized CmBAM has improved thermostability by 15-20 °C, which can lead to wider applications and easier handling.

Biodegradation effects of o-cresol by Pseudomonas monteilii SHY on mustard seed germination

Cresols are ubiquitous due to industrial production and natural presence. o-cresol (2-methyl phenol) is highly toxic to both fauna and flora. It has been included in the EPA list as one of the priority pollutants. The deleterious effects of pesticides, herbicides, and many other chemical compounds on seed germination are known. However, the effect of o-cresol on seed germination is not known. Therefore, it is of interest to study the effect of o-cresol on germination of 13 different vegetable crop seeds using standard Filter Paper Method. There is no effect on germination for brinjal, red chili, and (green gram, chickpea, cucumber, tomato, fenugreek, cowpea, Green pea, coriander, and spinach, seeds even at 1500 mg/l of o-cresol However, okra and mustard were found to be sensitive to ocresol. Germination of mustard under controlled concentration of o-cresol showed similar results by soil method. It was found that germination percentage and seedling vigour (Vigour Index) was reduced by o-cresol. The percent germination was reduced to 64 and 12 at 25 and 50 mg o-cresol/kg soil as against 100% in the case of untreated control. The vigour index was reduced to 160 and 10, respectively as against of 646 that for the control. The viability of seeds by 2,3,5 - tetrazolium trichloride (TTC) test showed that a considerable reduction was observed at 200mg/l o-cresol. Reduced protease and amylase activity in o-cresol shows inhibited mustard generation. However, mustard generation inhibition was restored by the bioremediation of o-cresol using Pseudomonas monteilii SHY. Thus, the biodegradation effects of o-cresol by Pseudomonas monteilii SHY on mustard seed germination are shown.

An antioxidant rich novel β-amylase from peanuts (Arachis hypogaea): Its purification, biochemical characterization and potential applications

β-Amylase from un-germinated seeds of peanut (Arachis hypogaea) was purified to apparent electrophoretic homogeneity with final purification fold of 205 and specific activity of 361μmol/min/mg protein. The enzyme was purified employing simple purification techniques for biochemical characterization. The purified enzyme was identified as β-amylase with M_r of 31kDa. The enzyme displayed its optimum catalytic activity at pH5.0 and 60°C with activation energy of 4.5kcal/mol and Q₁₀ 1.2. The enzyme displayed K_m and V_max values, for soluble potato starch of 1.28mg/mL and 363.63μmol/min/mg, respectively. Thermal inactivation of β-amylase at 65°C resulted into first-order kinetics with rate constant 0.0126min^-1 and t_½ 55min. The enzyme was observed to act on native granular potato starch, which could minimize the high cost occurring from solubilization of starch in industries. Enzyme fractions scavenge 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical, indicating its antioxidative nature. In addition, the purified β-amylase was successfully utilized for the improvement of antioxidant potential of wheat. These findings suggest that β-amylase from peanuts have potential application in food and pharmaceutical industries.

Extraction and purification of beta-amylase from stems of Abrus precatorius by three phase partitioning

The stems of Abrus precatorius were used to extract a beta-amylase enriched fraction. A three phase partitioning method and a Doehlert design with 3 variables (ratio of crude extract/t-butanol, the ammonium sulphate saturation and pH) were used. The data was fitted in a second-order polynomial model and the parameters were optimized to enrich beta-amylase. Experimental responses for the modulation were recovery of activity and the purification factor. The optimal conditions were: a ratio of crude extract/t-butanol of 0.87 (v/v), saturation in ammonium sulphate of 49.46% (w/v) and a pH of 5.2. An activity recovery of 156.2% and a purification factor of 10.17 were found. The enriched enzyme was identified as a beta-amylase and its molecular weight was 60.1kDa. Km and Vmax values were 79.37mg/ml and 5.13U/ml, respectively and the highest activity was registered at a temperature of 70°C and a pH between 6 and 6.5. A significant stabilization of the beta-amylase was observed up to 65°C.

Purification and characterization of midgut α-amylase in a predatory bug, Andralus spinidens

α-Amylases are widespread enzymes that catalyze endohydrolysis of long α-1,4-glucan chains such as starch and glycogen. The highest amylolytic activity was found in 5th instar nymphs and midgut of the predatory bug, Andrallus spinidens F. (Hemiptera: Pentatomidae). The α-amylase was purified following a three-step procedure. The purified α-amylase had a specific activity of 13.46 U/mg protein, recovery of 4.21, purification fold of 13.87, and molecular weight of 21.3 kDa. The enzyme had optimal pH and temperature of 7 and 45°C, respectively. Na+, Mn+, Mg2+, and Zn2+ significantly decreased activity of the purified α-amylase, but some concentrations of K+, Ca2+, and Cu2+ had the opposite effect. EDTA, EGTA, and DTC significantly decreased enzymatic activity, showing the presence of metal ions in the catalytic site of the enzyme. Kinetic parameters of the purified α-amylase showed a Km of 3.71% in starch and 4.96% for glycogen, suggesting that the enzyme had a higher affinity for starch.

Enzymatic conversions of starch

This article surveys methods for the enzymatic conversion of starch, involving hydrolases and nonhydrolyzing enzymes, as well as the role of microorganisms producing such enzymes. The sources of the most common enzymes are listed. These starch conversions are also presented in relation to their applications in the food, pharmaceutical, pulp, textile, and other branches of industry. Some sections are devoted to the fermentation of starch to ethanol and other products, and to the production of cyclodextrins, along with the properties of these products. Light is also shed on the enzymes involved in the digestion of starch in human and animal organisms. Enzymatic processes acting on starch are useful in structural studies of the substrates and in understanding the characteristics of digesting enzymes. One section presents the application of enzymes to these problems. The information that is included covers the period from the early 19th century up to 2009.

Structure and enzyme properties of Zabrotes subfasciatus alpha-amylase

Digestive alpha-amylases play an essential role in insect carbohydrate metabolism. These enzymes belong to an endo-type group. They catalyse starch hydrolysis, and are involved in energy production. Larvae of Zabrotes subfasciatus, the Mexican bean weevil, are able to infest stored common beans Phaseolus vulgaris, causing severe crop losses in Latin America and Africa. Their alpha-amylase (ZSA) is a well-studied but not completely understood enzyme, having specific characteristics when compared to other insect alpha-amylases. This report provides more knowledge about its chemical nature, including a description of its optimum pH (6.0 to 7.0) and temperature (20-30 degrees C). Furthermore, ion effects on ZSA activity were also determined, showing that three divalent ions (Mn2+, Ca2+, and Ba2+) were able to enhance starch hydrolysis. Fe2+ appeared to decrease alpha-amylase activity by half. ZSA kinetic parameters were also determined and compared to other insect alpha-amylases. A three-dimensional model is proposed in order to indicate probable residues involved in catalysis (Asp204, Glu240, and Asp305) as well other important residues related to starch binding (His118, Ala206, Lys207, and His304).

Purification and characterization of an alpha-glucosidase from germinating millet seeds

An alpha-glucosidase (alpha-D-glucoside glucohydrolase, EC 3.2.1.20) was isolated from germinating millet (Panicum miliaceum L.) seeds by a procedure that included ammonium sulfate fractionation, chromatography on CM-cellulofine/Fractogel EMD SO(3), Sephacryl S-200 HR and TSK gel Phenyl-5 PW, and preparative isoelectric focusing. The enzyme was homogenous by SDS-PAGE. The molecular weight of the enzyme was estimated to be 86,000 based on its mobility in SDS-PAGE and 80,000 based on gel filtration with TSKgel super SW 3000, which showed that it was composed of a single unit. The isoelectric point of the enzyme was 8.3. The enzyme readily hydrolyzed maltose, malto-oligosaccharides, and alpha-1,4-glucan, but hydrolyzed polysaccharides more rapidly than maltose. The K(m) value decreased with an increase in the molecular weight of the substrate. The value for maltoheptaose was about 4-fold lower than that for maltose. The enzyme preferably hydrolyzed amylopectin in starch, but also readily hydrolyzed nigerose, which has an alpha-1,3-glucosidic linkage and exists as an abnormal linkage in the structure of starch. In particular, the enzyme readily hydrolyzed millet starch from germinating seeds that had been degraded to some extent.