Assessment of Anti-aging Efficacy of the Master Antioxidant Glutathione

A chief tripeptide antioxidant Glutathione (GSH) is present inside each body cell which may have a profound effect in the control of aging. The anti-aging potency of GSH and its role towards the progression of certain age-related disease is still unclear. Glutathione based articles were searched on PubMEd database since the very first study of glutathione related to its discovery in 1923 to its present status till 2016. The data was made more informative and precise by searching glutathione relevant reports on google. Those articles were selected which were indicating the association of glutathione with the progression of age-related diseases, pre-clinical and clinical studies and age-longevity effect. It was analyzed that the increased oxidative stress (elevated GSSG/GSH ratio) is responsible for the incidence of age-related diseases and different organs failure. The glutathione redox ratio (GSSG/GSH) was found to be more pro-oxidizing with aging which plays a chief role for the generation of reactive oxygen species (ROS) and subsequently damages the macromolecular structures affecting the normal body mechanisms and functions. The clinical data has recommended that glutathione is a potent therapeutic agent for the control of age-related diseases and experimental analysis has confirmed its prominent effect in age-longevity

Decadal terminus position changes and ice thickness measurement of Menthosa Glacier in Lahaul region of North-Western Himalaya

Glacier ice-thickness measurement and distribution is one of the essential variables to assess present status of glacier-water equivalent and its volumetric reserve as well as to model the future glacier dynamics under the climate changing scenario. Yet, substantial gaps in ice thickness information exist for the Himalayan glaciers. The present study provides a long-term assessment (1965–2016) of recessional and area change patterns, as well as the detailed field-based (2016–2017) Ground Penetrating Radar(GPR), derived ice-thickness measurement of the Menthosa Glacier, Lahaul Himalaya. Additionally, the study examines whether the modelled ice thickness from remote sensing data is consistent with the field-based GPR measurement and how can it be improved. The extensive field surveys coupled with the multi-temporal high (Corona KH-4A) to medium resolution (Landsat Enhanced Thematic Mapper+ (ETM+)/Operational Land Imager (OLI), Sentinel 2A-Multispectral Instrument (MSI)) remote sensing data and cross-sectional GPR surveyed profile measurements have been used to examine past half a century (1965–2016) glacier fluctuation and the recent ice-thickness estimations, respectively. The results show that the Menthosa Glacier receded by 301.5 ± 19.2 m during the past half a century (1965–2016) with an average annual retreat of 5.9 ± 0.4 m a−1, whereas glacier lost 0.09 km2 ice in the frontal section. Field measurement over the past one decade (2006–2017) also conforms to a continuous recessional pattern and substantial glacier degeneration particularly the extensive surface lowering and significant appearance of ice-cliffs in the ablation and lateral zones over this period. The GPR measurements (2017) show the minimum glacier ice thickness of 24 meters at 4691 m a.s.l. (in the lower part of ablation area) and maximum glacier ice thickness of 55 meters measured at 4758 m a.s.l. (in the upper left-side tributary part of ablation area). Moreover, the modelled ice thickness derived from remotely sensed data is having Root Mean Square Error (RMSE) between 38 to 72 ± 10 m as compared with GPR measured ice thickness

Mutational analysis of the active-site residues crucial for catalytic activity of adenosine kinase from Leishmania donovani

Leishmania donovani adenosine kinase (LdAdK) plays a pivotal role in scavenging of purines from the host. Exploiting interspecies homology and structural co-ordinates of the enzyme from other sources, we generated a model of LdAdK that led us to target several amino acid residues (namely Gly-62, Arg-69, Arg-131 and Asp-299). Replacement of Gly-62 with aspartate caused a drastic reduction in catalytic activity, with decreased affinity for either substrate. Asp-299 was found to be catalytically indispensable. Mutation of either Arg-131 or Arg-69 caused a significant reduction in k(cat). R69A (Arg-69→Ala) and R131A mutants exhibited unaltered K(m) for either substrate, whereas ATP K(m) for R69K increased 6-fold. Importance of both of the arginine residues was reaffirmed by the R69K/R131A double mutant, which exhibited approx. 0.5% residual activity with a large increase in ATP K(m). Phenylglyoxal, which inhibits the wild-type enzyme, also inactivated the arginine mutants to different extents. Adenosine protected both of the Arg-69 mutants, but not the R131A variant, from inactivation. Binding experiments revealed that the AMP-binding property of R69K or R69A and D299A mutants remained largely unaltered, but R131A and R69K/R131A mutants lost their AMP binding ability significantly. The G62D mutant did not bind AMP at all. Free energy calculations indicated that Arg-69 and Arg-131 are functionally independent. Thus, apart from the mandatory requirement of flexibility around the diglycyl (Gly-61–Gly-62) motif, our results identified Asp-299 and Arg-131 as key catalytic residues, with the former functioning as the proton abstractor from the 5′-OH of adenosine, while the latter acts as a bidentate electrophile to stabilize the negative charge on the leaving group during the phosphate transfer. Moreover, the positive charge distribution of Arg-69 probably helps in maintaining the flexibility of the α-3 helix needed for proper domain movement. These findings provide the first comprehensive biochemical evidence implicating the mechanistic roles of the functionally important residues of this chemotherapeutically exploitable enzyme

Homology-model-guided site-specific mutagenesis reveals the mechanisms of substrate binding and product-regulation of adenosine kinase from Leishmania donovani

Despite designating catalytic roles of Asp(299) and Arg(131) during the transfer of γ-phosphate from ATP to Ado (adenosine) [R. Datta, Das, Sen, Chakraborty, Adak, Mandal and A. K. Datta (2005) Biochem. J. 387, 591–600], the mechanisms that determine binding of substrate and cause product inhibition of adenosine kinase from Leishmania donovani remained unclear. In the present study, employing homology-model-guided site-specific protein mutagenesis, we show that Asp(16) is indispensable, since its replacement with either valine or arginine resulted in a >200-fold increase in K(m) (Ado) with a 1000-fold decrease in k(cat)/K(m), implying its critical importance in Ado binding. Even glutamate replacement was not tolerated, indicating the essentiality of Asp(16) in the maintenance of steric complementarity of the binding pocket. Use of 2′or 3′-deoxygenated Ado as substrates indicated that, although both the hydroxy groups play important roles in the formation of the enzyme–Ado complex, the binding energy (ΔΔG(B)) contribution of the former was greater than the latter, suggesting possible formation of a bidentate hydrogen bond between Asp(16) and the adenosyl ribose. Interestingly, AMP-inhibition and AMP-binding studies revealed that, unlike the R131A mutant, which showed abrogated AMP-binding and insensitivity towards AMP inhibition despite its unaltered K(m) (Ado), all the Asp(16) mutants bound AMP efficiently and displayed AMP-sensitive catalytic activity, suggesting disparate mechanisms of binding of Ado and AMP. Molecular docking revealed that, although both Ado and AMP apparently occupied the same binding pocket, Ado binds in a manner that is subtly different from AMP binding, which relies heavily on hydrogen-bonding with Arg(131) and thus creates an appropriate environment for competition with Ado. Hence, besides its role in catalysis, an additional novel function of the Arg(131) residue as an effector of product-mediated enzyme regulation is proposed