Sathyanarayana N. Gummadi

Bio: Sathyanarayana N. Gummadi is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Phospholipid scramblase & Caffeine. The author has an hindex of 25, co-authored 139 publications receiving 2332 citations. Previous affiliations of Sathyanarayana N. Gummadi include Indian Institutes of Technology & University of Wisconsin-Madison.

pH-Dependent Thermal Stability of Vibrio cholerae L-asparaginase.

Abstract: BACKGROUND pH is one of the decisive macromolecular properties of proteins that significantly affects enzyme structure, stability and reaction rate. Change in pH may protonate or deprotonate the side group of aminoacid residues in the protein, thereby resulting in changes in chemical and structural features. Hence studies on the kinetics of enzyme deactivation by pH are important for assessing the bio-functionality of industrial enzymes. L-asparaginase is one such important enzyme that has potent applications in cancer therapy and food industry. OBJECTIVE The objective of the study is to understand and analyze the influence of pH on deactivation and stability of Vibrio cholerae L-asparaginase. METHODS Kinetic studies were conducted to analyze the effect of pH on stability and deactivation of Vibrio cholerae L-asparaginase. Circular Dichroism (CD) and Differential Scanning Calorimetry (DSC) studies have been carried out to understand the pH-dependent conformational changes in the secondary structure of V. cholerae L-asparaginase. RESULTS The enzyme was found to be least stable at extreme acidic conditions (pH< 4.5) and exhibited a gradual increase in melting temperature from 40 to 81 °C within pH range of 4.0 to 7.0. Thermodynamic properties of protein were estimated and at pH 7.0 the protein exhibited ΔG37of 26.31 kcal mole-1, ΔH of 204.27 kcal mole-1 and ΔS of 574.06 cal mole-1 K-1. CONCLUSION The stability and thermodynamic analysis revealed that V. cholerae L-asparaginase was highly stable over a wide range of pH, with the highest stability in the pH range of 5.0-7.0.

Biochemical evidence for Ca2+-independent functional activation of hPLSCR1 at low pH.

Abstract: Human phospholipid scramblase 1 (hPLSCR1) is a Ca2+-dependent protein known to scramble phospholipids in the plasma membrane resulting in loss of membrane asymmetry It has been reported that hPLSCR1 exhibits Ca2+- independent activity at low pH However, the conformational changes induced at low pH leading to functional activation are not known Our results showed that recombinant hPLSCR1 was functionally activated at low pH, which is similar to the behavior of natively extracted hPLSCR1 Tryptophan fluorescence measurements showed a decrease in Ca2+-binding affinity at low pH, although not at pH 55 Far and near UV-CD revealed that low pH induced structural changes, with a significant increase in the β-sheet content of the protein At the physiological level, decreased hPLSCR1 expression was observed after a period of exposure to low pH The effect occurred at the promoter level The expression levels of hPLSCR1 directly correlated with the sensitivity of HEK293 to apoptosis Based on these results, we conclude that the mechanisms of Ca2+- and pH-induced functional activation of hPLSCR1 are different and that hPLSCR1 expression regulated by low pH could provide insights into the role of hPLSCR1 in cancer progression

Characteristics of PM from Different South Indian Cooking Methods and Implications in Health Effects

Abstract: Indoor air pollution (IAP) predominantly contributed from biomass burning in rural households is a major health hazard. Cooking activities are significant sources of indoor particulate matter (PM). The present study focuses on characterising PM emissions from different cooking methods that are primarily prepared in rural areas of South India, in a simulated kitchen relying on biomass as fuel and estimation of respiratory dosage. Controlled experiments were carried out to study PM concentrations generated while performing different cooking methods including boiling (rice, urad dal and preparation of tea) and pan-frying (wheat roti and omlette). Multiple Particle Path Dosimetry (MPPD) was used to estimate deposition fractions in head, tracheobronchial and pulmonary regions of the human respiratory tract (HRT) for women. Further, PM dosage was assessed by entering the captured PM measurements and evaluated amongst different cooking methods. PM concentrations from pan-frying were ~1.6 times greater than boiling, primarily due to usage of oil for frying. Furthermore, pan-frying displayed higher dosage (412–2240 µg) compared to the boiling (258–1119 µg). However, urad dal displayed extreme amplification of 8.7 times than preparation of tea due to longer cooking duration. It is evident from above results that cooking methods are major attributes impacting IAP in rural areas with severe health impacts.

Bacterial extracellular polysaccharides involved in biofilm formation.

Abstract: Extracellular polymeric substances (EPS) produced by microorganisms are a complex mixture of biopolymers primarily consisting of polysaccharides, as well as proteins, nucleic acids, lipids and humic substances. EPS make up the intercellular space of microbial aggregates and form the structure and architecture of the biofilm matrix. The key functions of EPS comprise the mediation of the initial attachment of cells to different substrata and protection against environmental stress and dehydration. The aim of this review is to present a summary of the current status of the research into the role of EPS in bacterial attachment followed by biofilm formation. The latter has a profound impact on an array of biomedical, biotechnology and industrial fields including pharmaceutical and surgical applications, food engineering, bioremediation and biohydrometallurgy. The diverse structural variations of EPS produced by bacteria of different taxonomic lineages, together with examples of biotechnological applications, are discussed. Finally, a range of novel techniques that can be used in studies involving biofilm-specific polysaccharides is discussed.

The distribution and function of phosphatidylserine in cellular membranes.

Abstract: Phosphatidylserine (PS) is the most abundant negatively charged phospholipid in eukaryotic membranes. PS directs the binding of proteins that bear C2 or gamma-carboxyglutamic domains and contributes to the electrostatic association of polycationic ligands with cellular membranes. Rather than being evenly distributed, PS is found preferentially in the inner leaflet of the plasma membrane and in endocytic membranes. The loss of PS asymmetry is an early indicator of apoptosis and serves as a signal to initiate blood clotting. This review discusses the determinants and functional implications of the subcellular distribution and membrane topology of PS.