Amylase

About: Amylase is a research topic. Over the lifetime, 14164 publications have been published within this topic receiving 296069 citations.

Starch Biosynthesis and Degradation

Abstract: Publisher Summary This chapter presents the information known about starch biosynthesis and degradation, and the regulatory phenomena associated with it in leaf and in storage tissue. It also presents at least three possible enzymatic routes from glucose-1-P to the biosynthesis of α 1 - 4 glucosidic linkages in plant systems: the phosphorylase route, via UDP-glucose, or via ADP-glucose. Furthermore, many plant cell extracts contain potent amylase activities that can interfere with the starch synthase assay. The products of starch degradation comprise a major portion of the metabolites of germinating seeds or other reserve tissue that it is relatively straightforward to determine the major products of starch degradation in these tissues. However, in photosynthetic tissues, where starch degradation accounts for only part of the sugar, sugar phosphate and organic acid transformations occurring in the dark, it is more difficult to assign the appearance of intermediates to starch breakdown. Additionally, starch degradation in leaves may be regulated by phosphate concentration.

Production of amylase by the intestinal microflora in cultured freshwater fish

Abstract: The amylase-producing ability of the intestinal microflora in cultured specimens of ayu, carp, channel catfish, Japanese eel and tilapia was determined. Mean viable counts of aerobes and anaerobes ranged from 1.1 x 10 6 to 3.7 x 10 8 cfu g -1 and from 1.3 x 10 3 to 1.6 x 10 8 cfu g -1 , respectively. piermufias spp. and Bacteroidaceae were predominant in four to five fish species. Of 206 strains examined, 65 (31.6%) produced > 0.01 U amylase ml -1 . The percentage of producers differed among families and genera of bacteria and fish species. While 56% of the anaerobes produced amylase, only. 20% of the aerobes did. More than 50% of Aeromonas, Bacteroidaceae and Clostridium strains produced amylase efficiently while Acinetobacter, coryneforms, Enterobacteriaceae, Moraxella, Plesiomonas and Streptococcus strains did not. High amylase production (> 0.05 U ml -1 ) was found in 12 strains, 11 from Aeromonoas and one Pseudomonas. The percentage of high amylase producers in Japanese eel was lower than the other four fish (2-30%). These results strongly suggest that the amylase produced by the intestinal microflora play an important role in the digestion of starch in freshwater fish to some extent.

β-amylase 1 (BAM1) degrades transitory starch to sustain proline biosynthesis during drought stress

Abstract: During photosynthesis of higher plants, absorbed light energy is converted into chemical energy that, in part, is accumulated in the form of transitory starch within chloroplasts. In the following night, transitory starch is mobilized to sustain the heterotrophic metabolism of the plant. β-amylases are glucan hydrolases that cleave α-1,4-glycosidic bonds of starch and release maltose units from the non-reducing end of the polysaccharide chain. In Arabidopsis, nocturnal degradation of transitory starch involves mainly β-amylase-3 (BAM3). A second β-amylase isoform, β-amylase-1 (BAM1), is involved in diurnal starch degradation in guard cells, a process that sustains stomata opening. However, BAM1 also contributes to diurnal starch turnover in mesophyll cells under osmotic stress. With the aim of dissecting the role of β-amylases in osmotic stress responses in Arabidopsis, mutant plants lacking either BAM1 or BAM3 were subject to a mild (150mM mannitol) and prolonged (up to one week) osmotic stress. We show here that leaves of osmotically-stressed bam1 plants accumulated more starch and fewer soluble sugars than both wild-type and bam3 plants during the day. Moreover, bam1 mutants were impaired in proline accumulation and suffered from stronger lipid peroxidation, compared with both wild-type and bam3 plants. Taken together, these data strongly suggest that carbon skeletons deriving from BAM1 diurnal degradation of transitory starch support the biosynthesis of proline required to face the osmotic stress. We propose the transitory-starch/proline interplay as an interesting trait to be tackled by breeding technologies aimingto improve drought tolerance in relevant crops.

Characterization of physical properties of flour and starch obtained from gamma-irradiated white rice

Abstract: Physical and structural characteristics of rice flour and starch obtained from gamma-irradiated white rice were determined. Pasting viscosities of the rice flour and starch, analyzed by using a Rapid Visco Analyser, decreased continuously with the increase in irradiation dosage. Differential scanning calorimetry showed that gelatinization onset, peak and conclusion temperatures of rice flour and starch changed slightly but the enthalpy change decreased significantly with increase of irradiation dosage. All irradiated starch displayed an A-type X-ray diffraction pattern like the native starch. Gel permeation chromatography showed that the blue value ratio of the first peak (amylopectin) to the second one (amylose) decreased with the increase of the irradiation dosage. The weight-average molecular weight (M w ) and gyration radius (R z ) of amylopectin analyzed by using HPSEC-MALLS-RI (high-performance size-exclusion chromatography equipped with multiangle laser-light scattering and refractive index detector) decreased gradually from 1.48 x 10 9 (M w ) and 384.1 nm (R z ) of native rice starch to 2.36 × 10 8 (M w ) and 236.8 nm of 9 kGy-irradiated starch. The branch chain-length distribution of amylopectins determined by HPAEC-ENZ-PAD (high-performance anion-exchange chromatography with amyloglucosidase post-column on-line reactor and pulsed amperometric detector) showed that gamma irradiation had no significant effect on the amylopectin branch chains with 13