Polymorphism and pedigree analysis of β-amylase isozymes in Australian wheat

Studying of the promotion mechanism of Bacillus subtilis QM3 on wheat seed germination based on β-amylase

The response of β-amylase in early stage germination of wheat seeds to Bacillus subtilis QM3 was mainly focused on to elucidate the promotion mechanism of B. subtilis QM3. The results showed that the changes in apparent activity of amylase and endosperm liquefaction after the strain QM3 treatment were much more obvious than that of the control group; the activity of β-amylase treated with the different concentrations of the strain QM3 increased significantly (P < 0.05) by 4% (10⁷ CFU/mL) and 18.5% (10⁶ CFU/mL) at the germination 6 h. Moreover, after presoaking with α-cyclodextrin, the activity of β-amylase increased significantly (P < 0.05) by 18.5% (10⁷ CFU/mL) and 23.4% (10⁶ CFU/mL) at the same stage of germination; the electrophoretogram of β-amylase isoenzymes showed that there is a growing trend in brightness and width of the band during the early germination from 3 to 6 h of wheat seed treated by the strain QM3 (10⁶ CFU/mL). The increase in activity and isoenzyme expression of β-amylase may be one of the important reasons to promote the germination of wheat seeds after being treated by B. subtilis QM3.

Prediction and analysis of GH14 family β-amylases in oat seedling extract: Structure and function insights using in silico approaches

Oat (Avena sativa L.) seedling extract exhibited a high degree of catalytic activities. Bioinformatics were used to identify β-amylases as abundant enzymes in the oat seedling extract. These identified oat enzymes are a member of the GH14 family. Proteins in the Avena sativa seedling extract were separated by SDS-PAGE and 2 major protein bands with an apparent molecular weights of 53 and 42 kDa were the subject of this study. These materials were digested with trypsin and the amino acid sequences of the tryptic peptides were determined by LC/ESI/MS/MS and database searches. These sequences were used to identify cDNAs from expressed sequence tags (EST) and Transcriptome Shotgun Assembly (TSA) of Avena sativa. Based upon EST and TSA sequences, at least 6 predicted different sequences were identified and assigned as β-amylases. Insights into structural characterization of the oat predicted β-amylases were analyzed using in silico approaches. The identified β-amylases conserved the two Glu residues assigned as the "putative" catalytic residues, which would act as an acid and base pair in the catalytic process. A similar core (β/α)₈-barrel architecture was found in the predicted oat β-amylases with a specific location of the active site in a pocket-like cavity structure made at one end of this core (β/α)₈-barrel domain. This suggests an accessibility of the non-reducing end of the substrate towards the oat β-amylases and thus confirming that are exo-acting hydrolases. The results provide a detailed view of the main residues involved in catalysis in this kind of enzyme.

Characterization of thermostable β-amylase isozymes from Lactobacillus fermentum

A strain of Lactobacillus fermentum producing two isozymes of a 20kDa β-amylase was isolated from the faecal sample of a newborn. The starin was identified by sequencing its 16S rRNA gene. The two β-amylase isozymes were resolved and visualized by two dimensional protein gel electrophoresis (2-D gel electrophoresis). Some of the physical and biochemical properties of the enzymes were characterized. The β-amylase displayed two optimum pH s, 5.0 and 10.0 and two optimum temperatures, 45°C and 37°C, respectively. The isozymes hydrolyzed different substrates: glycogen at pH 5.0, and corn starch at pH 10.0. The activity did not require Ca²⁺, though the activity at pH 10.0 was enhanced in the presence of 5.0mM and 10.0mM CaCl_2, 110% and 130%, respectively.

Identification of a protein with antioxidant activity that is important for the protection against beer ageing

This study was carried out with fresh Australian lager beer which was sampled directly off the production line, the same samples aged for 12 weeks at 30 °C, and the vintage beer which was kept at 20 °C for 5 years. Characteristic Australian lager flavour was maintained in the fresh and vintage beers but was lost in the aged beer. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and free thiol group labelling analyses of beer proteins found that this flavour stability correlated with the presence of an unknown 10 kilodaltons (kDa) protein with a higher level of free thiols. The protein was purified by size-exclusion chromatography, then peptide sequencing and database matching identified it as the barley lipid transfer protein (LTP1). Further characterisation using diphenylpicrylhydrazyl (DPPH) free radical scavenging and a Saccharomyces cerevisiae-based antioxidant screening assay demonstrated that the LTP1 protein was active in DPPH reduction and antioxidant activity. The absence of free thiol in the aged beer indicates that the thiol functional groups within the LTP1 protein were saturated and suggests that it is important in the flavour stability of beer by maintaining reduction capacity during the ageing process.