Gamma-glutamyl transpeptidase (GGT) enzyme is ubiquitously present in all life forms and plays a ... more Gamma-glutamyl transpeptidase (GGT) enzyme is ubiquitously present in all life forms and plays a variety of roles in diverse organisms. Higher eukaryotes mainly utilize GGT for glutathione degradation, and mammalian GGTs have implications in many physiological disorders also. GGTs from unicellular prokaryotes serve different physiological functions in Gram-positive and Gram-negative bacteria. In the present review, the physiological significance of bacterial GGTs has been discussed categorizing GGTs from Gram-negative bacteria like Escherichia coli as glutathione degraders and from pathogenic species like Helicobacter pylori as virulence factors. Gram-positive bacilli, however, are considered separately as poly-γ-glutamic acid (PGA) degraders. The structure–function relationship of the GGT is also discussed mainly focusing on the crystallization of bacterial GGTs along with functional characterization of conserved regions by site-directed mutagenesis that unravels molecular aspects ...
Today indiscriminate and uncontrolled discharge of metal contaminated industrial effluents into t... more Today indiscriminate and uncontrolled discharge of metal contaminated industrial effluents into the environment has become an issue of major concern. Heavy metals, being non-biodegradable and persistent, beyond a permissible concentration form unspecific compounds inside the cells thereby causing cellular toxicity. The only alternative to remove them from the wastewater is by immobilizing them. The conventional methods adopted earlier for this purpose included chemical precipitation, oxidation, reduction, filtration, electrochemical treatment, evaporation, adsorption and ion-exchange resins. These methods require high energy inputs especially when it refers to dilute solutions. Here microbial biomass offers an economical option for removing heavy metals by the phenomenon of biosorption. Non-living or dead biomass sequester metal(s) on their cell surface due to certain reactive groups available like carboxyl, amine, imidazole, phosphate, sulphydryl, sulfate and hydroxyl. The process ...
Since polyamines (PAs) play a potential role in the regulation of growth and developmental proces... more Since polyamines (PAs) play a potential role in the regulation of growth and developmental processes in a wide variety of organisms, we have examined the influence of the PAs putrescine (Put) and spermidine (Spd) and the PA biosynthetic inhibitors α-difluoromethylornithine (DFMO), α-difluoromethylarginine (DFMA), methylglyoxal bis-(guanylhydrazone) (MGBG) and cyclohexylamine (CHA), singly and in combinations on microcycle conidiation (MC) in Aspergillus flavus. The exogenous application of the diamine Put (concentrations ranging from 0·1 to 5 mM) caused a sharp decline of MC in a dose-dependent fashion, but induced vegetative growth. However, the triamine Spd (0·1-5 mM) had a minimal effect on MC and induced a shift from MC to normal conidiation. PA inhibitors, especially DFMO, MGBG and CHA, produced greater inhibition of MC and complete inhibition of MC was observed at 5 mM of these inhibitors. DFMA even at 5 mM had only a weak inhibitory effect on MC. DFMO also inhibited conidial ...
International journal of biological macromolecules, Jan 2, 2017
Biodiesel, an environment friendly alternative for fuels, contains methyl esters of long-chain fa... more Biodiesel, an environment friendly alternative for fuels, contains methyl esters of long-chain fatty acids. Our group has reported a methanol-stable YLIP9 from Yarrowia lipolytica MSR80 that shows poor catalysis of long-chain fatty acids. To shift its substrate specificity, residues within lid and binding pocket were identified for sequential mutations using YLIP2 as the template. Of the two point mutations (Glu116Leu and Ser119Val) introduced in the lid, the former mutation (YLIP9L1) increased the catalytic rate by ∼2-fold without any change in substrate specificity. In this mutant, six binding pocket residues (Bp2-Bp7) were further mutated to obtain six double mutants. YLIP9L1Bp3 showed significant shift in substrate specificity towards long-chain pNPesters with 11-fold increase in catalytic efficiency than YLIP9. Double mutations also led to increased thermostability and lowered activation energy of YLIP9L1Bp3 thereby shifting its optimum temperature from 60°C to 50°C. In silico ...
An extracellular keratinase fromBacillus pumilusKS12 was purified by DEAE ion exchange chromatogr... more An extracellular keratinase fromBacillus pumilusKS12 was purified by DEAE ion exchange chromatography. It was a 45 kDa monomer as determined by SDS PAGE analysis. It was found to be an alkaline, serine protease with pH and temperature optima of 10 and 60C, respectively. It was thiol activated with two- and eight-fold enhancement in presence of 10 mM DTT andβ-mercaptoethanol, respectively. In addition, its activity was stimulated in the presence of various surfactants, detergents, and oxidizing agents where a nearly 2- to 3-fold enhancement was observed in presence ofH2O2andNaHClO3. It hydrolyzed broad range of complex substrates including feather keratin, haemoglobin, fibrin, casein,andα-keratin. Analysis of amidolytic activity revealed that it efficiently cleaved phenylalanine→leucine→alanine-p-nitroanilides. It also cleaved insulin B chain betweenVal2-Asn3,Leu6-Cys7andHis10-Leu11residues.
A hyper-thermostable, alkaline lipase from a newly-isolated, mesophilic Pseudomonas sp. was optim... more A hyper-thermostable, alkaline lipase from a newly-isolated, mesophilic Pseudomonas sp. was optimal at pH 11 and at 90 °C. It had a half-life of more than 13 h at 90 °C. It was activated by 30% when heated at 90 °C for 2 h. The enzyme had a greater affinity for mustard oil (Km=40 mg ml-1) than for olive oil
Gamma-glutamyl transpeptidase (GGT) enzyme is ubiquitously present in all life forms and plays a ... more Gamma-glutamyl transpeptidase (GGT) enzyme is ubiquitously present in all life forms and plays a variety of roles in diverse organisms. Higher eukaryotes mainly utilize GGT for glutathione degradation, and mammalian GGTs have implications in many physiological disorders also. GGTs from unicellular prokaryotes serve different physiological functions in Gram-positive and Gram-negative bacteria. In the present review, the physiological significance of bacterial GGTs has been discussed categorizing GGTs from Gram-negative bacteria like Escherichia coli as glutathione degraders and from pathogenic species like Helicobacter pylori as virulence factors. Gram-positive bacilli, however, are considered separately as poly-γ-glutamic acid (PGA) degraders. The structure–function relationship of the GGT is also discussed mainly focusing on the crystallization of bacterial GGTs along with functional characterization of conserved regions by site-directed mutagenesis that unravels molecular aspects ...
Today indiscriminate and uncontrolled discharge of metal contaminated industrial effluents into t... more Today indiscriminate and uncontrolled discharge of metal contaminated industrial effluents into the environment has become an issue of major concern. Heavy metals, being non-biodegradable and persistent, beyond a permissible concentration form unspecific compounds inside the cells thereby causing cellular toxicity. The only alternative to remove them from the wastewater is by immobilizing them. The conventional methods adopted earlier for this purpose included chemical precipitation, oxidation, reduction, filtration, electrochemical treatment, evaporation, adsorption and ion-exchange resins. These methods require high energy inputs especially when it refers to dilute solutions. Here microbial biomass offers an economical option for removing heavy metals by the phenomenon of biosorption. Non-living or dead biomass sequester metal(s) on their cell surface due to certain reactive groups available like carboxyl, amine, imidazole, phosphate, sulphydryl, sulfate and hydroxyl. The process ...
Since polyamines (PAs) play a potential role in the regulation of growth and developmental proces... more Since polyamines (PAs) play a potential role in the regulation of growth and developmental processes in a wide variety of organisms, we have examined the influence of the PAs putrescine (Put) and spermidine (Spd) and the PA biosynthetic inhibitors α-difluoromethylornithine (DFMO), α-difluoromethylarginine (DFMA), methylglyoxal bis-(guanylhydrazone) (MGBG) and cyclohexylamine (CHA), singly and in combinations on microcycle conidiation (MC) in Aspergillus flavus. The exogenous application of the diamine Put (concentrations ranging from 0·1 to 5 mM) caused a sharp decline of MC in a dose-dependent fashion, but induced vegetative growth. However, the triamine Spd (0·1-5 mM) had a minimal effect on MC and induced a shift from MC to normal conidiation. PA inhibitors, especially DFMO, MGBG and CHA, produced greater inhibition of MC and complete inhibition of MC was observed at 5 mM of these inhibitors. DFMA even at 5 mM had only a weak inhibitory effect on MC. DFMO also inhibited conidial ...
International journal of biological macromolecules, Jan 2, 2017
Biodiesel, an environment friendly alternative for fuels, contains methyl esters of long-chain fa... more Biodiesel, an environment friendly alternative for fuels, contains methyl esters of long-chain fatty acids. Our group has reported a methanol-stable YLIP9 from Yarrowia lipolytica MSR80 that shows poor catalysis of long-chain fatty acids. To shift its substrate specificity, residues within lid and binding pocket were identified for sequential mutations using YLIP2 as the template. Of the two point mutations (Glu116Leu and Ser119Val) introduced in the lid, the former mutation (YLIP9L1) increased the catalytic rate by ∼2-fold without any change in substrate specificity. In this mutant, six binding pocket residues (Bp2-Bp7) were further mutated to obtain six double mutants. YLIP9L1Bp3 showed significant shift in substrate specificity towards long-chain pNPesters with 11-fold increase in catalytic efficiency than YLIP9. Double mutations also led to increased thermostability and lowered activation energy of YLIP9L1Bp3 thereby shifting its optimum temperature from 60°C to 50°C. In silico ...
An extracellular keratinase fromBacillus pumilusKS12 was purified by DEAE ion exchange chromatogr... more An extracellular keratinase fromBacillus pumilusKS12 was purified by DEAE ion exchange chromatography. It was a 45 kDa monomer as determined by SDS PAGE analysis. It was found to be an alkaline, serine protease with pH and temperature optima of 10 and 60C, respectively. It was thiol activated with two- and eight-fold enhancement in presence of 10 mM DTT andβ-mercaptoethanol, respectively. In addition, its activity was stimulated in the presence of various surfactants, detergents, and oxidizing agents where a nearly 2- to 3-fold enhancement was observed in presence ofH2O2andNaHClO3. It hydrolyzed broad range of complex substrates including feather keratin, haemoglobin, fibrin, casein,andα-keratin. Analysis of amidolytic activity revealed that it efficiently cleaved phenylalanine→leucine→alanine-p-nitroanilides. It also cleaved insulin B chain betweenVal2-Asn3,Leu6-Cys7andHis10-Leu11residues.
A hyper-thermostable, alkaline lipase from a newly-isolated, mesophilic Pseudomonas sp. was optim... more A hyper-thermostable, alkaline lipase from a newly-isolated, mesophilic Pseudomonas sp. was optimal at pH 11 and at 90 °C. It had a half-life of more than 13 h at 90 °C. It was activated by 30% when heated at 90 °C for 2 h. The enzyme had a greater affinity for mustard oil (Km=40 mg ml-1) than for olive oil
Uploads
Papers by Rani Gupta