Khawar Sohail Siddiqui

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By far the largest proportion of the Earth's biosphere is comprised of organisms that thrive in cold environments (psychrophiles). Their ability to proliferate in the cold is predicated on a capacity to synthesize cold-adapted enzymes. These enzymes have evolved a range of structural features that confer a high level of flexibility compared to thermostable(More)
Genetic polymorphisms of DNA repair genes seem to determine the DNA repair capacity. We hypothesized that polymorphisms of genes responsible for DNA repair may be associated with risk of thyroid cancer. To evaluate the role of genetic polymorphisms of DNA repair genes in thyroid cancer, we conducted a hospital-based case-control study in Saudi population.(More)
Psychrophilic (cold-adapted) organisms and their products have potential applications in a broad range of industrial, agricultural and medical processes. In order for growth to occur in low-temperature environments, all cellular components must adapt to the cold. This fact, in combination with the diversity of Archaea, Bacteria and Eucarya isolated from(More)
The bulk of the Earth's biosphere is cold (e.g. 90% of the ocean's waters are ≤ 5°C), sustaining a broad diversity of microbial life. The permanently cold environments vary from the deep ocean to alpine reaches and to polar regions. Commensurate with the extent and diversity of the ecosystems that harbour psychrophilic life, the functional capacity of the(More)
Psychrophilic archaea are abundant and perform critical roles throughout the Earth's expansive cold biosphere. Here we report the first complete genome sequence for a psychrophilic methanogenic archaeon, Methanococcoides burtonii. The genome sequence was manually annotated including the use of a five-tiered evidence rating (ER) system that ranked(More)
Purified β-glucosidase fromCellulomonas biazotea had an apparentK m andV for 2-nitrophenyl β-d-glucopyranoside (oNPG) of 0.416 mmol/L and 0.22 U/mg protein, respectively. The activation energy for the hydrolysis of pNPG of β-glucosidase was 65 kJ/mol. The inhibition by Mn2+ vs. oNPG of parental β-glucosidase was of mixed type with apparent inhibition(More)
The activity-stability-structure relationship of the cold-active alkaline phosphatase from Red Arctic shrimp, Pandalus borealis (SAP) was studied by chemically modifying aliphatic (C-H) or amino (NH2) groups using benzophenone tetracarboxylic derivatives in either a light (UV-A) or dark reaction. The response of the cold-adapted enzyme was compared to a(More)
BACKGROUND FoxM1 has been shown to play a critical role in the pathogenesis of various epithelial malignancies. However, its role in lymphoid malignancies has not been fully clarified. We, therefore, investigated the role of FoxM1 expression in a large cohort of diffuse large B-cell lymphoma samples and panel of cell lines. DESIGN AND METHODS FoxM1(More)
We report the first characterization of an L-arginine:glycine amidinotransferase from a prokaryote. The enzyme, CyrA, is involved in the pathway for biosynthesis of the polyketide-derived hepatotoxin cylindrospermopsin from Cylindrospermopsis raciborskii AWT205. CyrA is phylogenetically distinct from other amidinotransferases, and structural alignment shows(More)
The carboxyl groups of purified carboxymethylcellulase (CMCase) from Aspergillus niger NIAB280 were modified by 1-ethyl-3(3-dimethylaminopropyl) carbodiimide (EDC) in the presence of glycinamide for 15 min (GAM15) and glycinamide plus cellobiose for 75 min (GAM75). The half-lives of GAM15 at different temperatures were significantly enhanced whereas those(More)