No abstract

Earlier, low-temperature-active polygalacturonase isoforms from PVK4 were isolated and purified. Substrate specificity of polygalacturonase isoforms indicated high affinity for pectins and very low enzyme activity towards non-pectic polysaccharides. To characterize the polygalacturonase isoforms, biochemical, spectral, and in silico approaches were used. The apparent and values for hydrolysis of pectin and galacturonic acid were 0.31 mg/ml and 3.15 mmol min/mg, respectively. Interestingly, the polygalacturonase isoforms were found to be more stable at optimal pH and temperature of 4.5 and 40 °C, respectively. These isoforms were reacted with different metal ions; Cd and Ni severely inhibited the enzyme activity, while Mg, Zn, Cd, Fe Cu, and Ni inhibited to a lesser extent, which clearly demonstrated that variations in enzyme activity were due to their differential binding affinity of metal ions. Furthermore, decrease in the viscosity of polygalacturonic acid and citrus pectin by these isoforms was approximately four and six times higher than the rate of release of reducing sugars. This indicates that polygalacturonase isoforms have an endo-mode of action. In addition to the above, thermostability of purified polygalacturonase isoforms was studied by circular dichroism and fluorescence spectroscopy. Circular dichroism showed 18% alpha helix and 57% beta sheets at pH 5, while at pH 7, 8, and 9 there was an increase of random coil. Fluorescence studies revealed small conformational changes, which were observed at 30-50 °C, while unfolding transition region was noticed between 60 and 70 °C. The purified enzyme fractions were analyzed by MALDI-TOF MS. Finally, 3D model structures for isoenzymes of polygalacturonase of were generated and validated as good quality models, which are also suitable for molecular interaction studies.

An endo-poly-galacturonase (PGU1) gene product is responsible for the pectolytic activity in Saccharomyces bayanus. Therefore, it is of interest to document the comparative structural and functional analysis of the PGU1 protein from Saccharomyces bayanus with those in other Saccharomyces related species. The molecular docking analyses of pectin with the different homology models of PGU1 protein from several Saccharomyces species are reported.

The microbial life indigenous to mineral deposits are generally regarded as extremophiles as they are tolerant to extreme conditions. The microorganisms that thrive in such environments survive by modifying their metabolic pathway or mechanisms. The microbiome associated with ore deposits remain poorly studied. The present study is the first attempt to explore the taxonomic composition of the bacterial community associated with the muscovite ore deposit from Southern India by using high throughput Illumina sequencing employing the V3 and V4 region of the16S rDNA and bioinformatics channel. A total of 20 bacterial phyla with 55 classes, 96 orders, 192 families, 382 genera and 462 species were recovered in the study. The alpha diversity index suggests that muscovite ore deposits harbored highly variable bacterial communities. Among the bacterial communities, Proteobacteria (33%), Actinobacteria (29.9%), Firmicutes (25.4%), Bacteroidetes (5.5%) and Chloroflexi (2.7%) were the dominate phyla. A total of 156 abundant species and 306 rare species were observed and is an indication of the presence of novel species. This study helps to understand the survival strategy of oligotrophs, which are an important aspect of microbial ecology.