Biology subjects

Syed, A.

Publications and source records attributed to Syed, A..

3 recordsLinked to original sources

bioRxiv2019

Thermophilic PHB depolymerase of Stenotrophomonas sp., an isolate from the plastic contaminated site is best purified on Octyl-Sepharose CL-4B

There are numerous reports on PHB depolymerases produced by a wide variety of microorganisms isolated from various habitats, however, reports on PHB depolymerase isolated from plastic contaminated sites are scares. Thermophilic PHB polymerase produced by isolates obtained from plastic contaminated sites is expected to have better relevance for its application in plastic/ bioplastic degradation. Although PHB has attracted commercial significance, the inefficient production and recovery methods, inefficient purification of PHB depolymerase and lack of ample knowledge on PHB degradation by PHB depolymerase have hampered its large scale commercialization. Therefore, to ensure the biodegradability of biopolymers, it becomes imperative to study the purification of the biodegrading enzyme system. We report the production, purification, and characterization of extracellular PHB depolymerase from Stenotrophomonas sp. RZS 7 isolated from a plastic contaminated site. The isolate produced extracellular poly-{beta}-hydroxybutyrate (PHB) depolymerase in the mineral salt medium at 30oC during 4 days of incubation under shake flask condition. Purification of the enzyme was carried out by three different methods using PHB as a substrate. Purification of PHB depolymerase by ammonium salt precipitation, column chromatography, and solvent purification method was successfully carried out. Among the purification method tested, the enzyme was best purified by column chromatography on Octyl-Sepharose CL-4B column with maximum (0.7993 U/mg/ml) purification yield. The molecular weight of purified PHB depolymerase (40 kDa) closely resembled with PHB depolymerase of Aureobacterium saperdae.

microbiology↗

bioRxiv2019

AGO1x prevents dsRNA-induced interferon signaling to promote breast cancer cell proliferation

Initially reported for viral RNA, elongation of polypeptide chains beyond the stop codon (translational readthrough (TR)) also occurs on eukaryotic transcripts. TR diversifies the proteome and can modulate protein levels 1-6. Here we report that AGO1x, a conserved TR isoform of Argonaute 1, is generated in highly proliferative breast cancer cells, where it curbs accumulation of double stranded RNAs, the induction of the interferon response and apoptosis. In contrast to other mammalian Argonaute protein family members with primarily cytoplasmic functions, AGO1x localizes to the nucleus, in the vicinity of nucleoli. We identify a novel interaction of AGO1x with the Polyribonucleotide Nucleotidyltransferase 1, depletion of either protein leading to dsRNA accumulation and impaired cell proliferation. Our study thus uncovers a novel function of an Argonaute protein outside of the miRNA effector pathway, in buffering dsRNA-induced interferon responses. As AGO1x expression is tightly linked to breast cancer cell proliferation, our study suggests a new direction for limiting tumor growth.

cell biology↗

bioRxiv2019

Production, purification, and kinetics of the poly-β-hydroxybutyrate depolymerase from Microbacterium paraoxydans RZS6: A novel biopolymer-degrading organism isolated from a dumping yard

Poly-{beta}-hydroxybutyrate (PHB) depolymerase can decompose biodegradable polymers and therefore has great commercial significance in the bioplastic sector. However, few reports have described PHB depolymerases based on isolates obtained from plastic-contaminated sites that reflect the potential of the source organism. In this study, we evaluated Microbacterium paraoxydans RZS6 as a producer of extracellular PHB depolymerase isolated from a plastic-contaminated site in the municipal area of Shahada, Maharashtra, India, for the first time. The isolate was identified using the polyphasic approach, i.e., 16S rRNA gene sequencing, gas chromatographic analysis of fatty acid methyl esters, and BIOLOG identification, and was found to hydrolyze PHB on minimal salt medium containing PHB as the only source of carbon. Both isolates produced PHB depolymerase at 30{degrees}C within 2 days and at 45{degrees}C within 4 days. The enzyme was purified most efficiently using an octyl-sepharose CL-4B column, with the highest purification yield of 6.675 U/mg/mL. The enzyme required Ce2+ and Mg2+ ions but was inhibited by Fe2+ ions and mercaptoethanol. Moreover, enzyme kinetic analysis revealed that the enzyme was a metalloenzyme requiring Mg2+ ions, with optimum enzyme activity at 45{degrees}C (thermophilic) and under neutrophilic conditions (optimum pH = 7). The presence of Fe2+ ions (1 mM) and mercaptoethanol (1000 ppm) completely inhibited the enzyme activity. The molecular weight of the enzyme (40 kDa), as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, closely resembled that of PHB depolymerase from Aureobacterium saperdae. Scale-up from the shake-flask level to a laboratory-scale bioreactor further enhanced the enzyme yield. Our findings highlighted the applicability of M. paraoxydans as a producer of extracellular PHB depolymerase isolated from a plastic-contaminated site in the municipal area of Shahada, Maharashtra, India.

microbiology↗