Development of superoxide dismutase based visual and spectrophotometric method for rapid differentiation of fresh and frozen-thawed buffalo meat.

Study aimed to develop biomarker-based assay for rapid detection of fresh and frozen-thawed buffalo meat in the supply chain. The method is based on development of a solvent system and identification of suitable substrate and developer for screening of biomarkers. For the confirmation column chromatography, gel electrophoresis and Western Blotting were carried out. Validation was done by intra- and inter-day validation, storability study, and determination of thermal history. Best results were shown with pH 8.0 Tris-HCl; extraction buffer, 205 µM nicotinamide adenine dinucleotide hydrogen; substrate, 184 µM Nitroblue tetrazolium, and 1.9 µM phenazine methosulfate; developer. The thermal history ranged from 0.14 to 0.17 during storage at -20 °C. The intra- and inter-day assay precision (CV %) ranged from 5.3 to 6.5 %; in chilled and 14.1 - 9.2 % in frozen-thawed samples. The study confirmed SOD as a viable biomarker. Developed method using SOD has significant potential for rapidly differentiating chilled or frozen-thawed meat.

Elucidation of kinetic and structural properties of eye lens ζ-crystallin: an in vitro and in silico approach.

The Arabian Camelus dromedarius contains significant concentration of eye lens ζ-crystallin. This enzyme is also present in other life forms including humans, however in lower catalytic amounts. The recombinant camel ζ-crystallin was expressed in the E. coli BL21 (DE3) pLysS strain and purified using HisTrap column. The Km of the enzyme for 9,10-phenanthrenequinone (9,10-PQ) substrate and NADPH cofactor was determined to be 11.66 and 50.93 µM, respectively. The Vmax for 9,10-PQ and NADPH was obtained as 23.19 and 19.98 µM min-1, respectively. The optimum activity of the purified enzyme was found to be at pH 6.0 and at 55 °C. Different physico-chemical parameters were analysed including instability index (II), aliphatic index (AI) and the GRAVY index to establish proper characterization. The sequence of the recombinant ζ-crystallin was subjected to homology modelling using SWISS-MODEL webserver followed by validation of the modelled target structure. The evaluation of the modelled ζ-crystallin was performed by several parameters including Ramachandran plot, Z-score values followed by molecular dynamics (MD) simulation. The cumulative analysis of the physico-chemical, quantitative, qualitative and the essential dynamics of simulation of ζ-crystallin and its complexes with 9,10-PQ and NADPH helped in verifying the acceptable quality and stability of the ζ-crystallin structure.Communicated by Ramaswamy H. Sarma.

A comparative study based on activity, conformation and computational analysis on the inhibition of human salivary aldehyde dehydrogenase by phthalate plasticizers: Implications in assessing the safety of packaged food items.

Phthalate plasticizers are commonly used in various consumer-end products. Human salivary aldehyde dehydrogenase (hsALDH) is a detoxifying enzyme which defends us from the toxic aldehydes. Here, the effect of phthalates [Di-2-ethylhexyl phthalate (DEHP), Diethyl phthalate (DEP) and Dibutyl phthalate (DBP)] on hsALDH has been investigated. These plasticizers inhibited hsALDH, and the IC50 values were 0.48 ± 0.04, 283.20 ± 0.09 and 285.00 ± 0.14 µM for DEHP, DEP and DBP, respectively. DEHP was the most potent inhibitor among the three plasticizers. They exhibited mixed-type linear inhibition with inclination towards competitive-non-competitive inhibition. They induced both tertiary and secondary structural changes in the enzyme. Quenching of intrinsic hsALDH fluorescence in a constant manner was observed with a binding constant (Kb) of 8.91 × 106, 2.80 × 104, and 1.31 × 105 M-1, for DEHP, DEP and DBP, respectively. Computational analysis showed that these plasticizers bind stably in the proximity of hsALDH catalytic site, reciprocating via non-covalent interactions with some of the amino acids which are evolutionary conserved. Therefore, exposure to these plasticizers inhibits hsALDH which increases the risk of aldehyde induced toxicity, adversely affecting oral health. The study has implications in assessing the safety of packaged food items which utilize phthalates.

Arsenic inhibits human salivary aldehyde dehydrogenase: Mechanism and a population-based study.

Human salivary aldehyde dehydrogenase (hsALDH) is an important detoxifying enzyme and maintains oral health. Subjects with low hsALDH activity are at a risk of developing oral cancers. Arsenic (As) toxicity causes many health problems in humans. The objective of this population-based study was to correlate As contamination and hence low hsALDH activity with high incidence of cancer cases in Bareilly district of India. Here, it was observed that As inhibited hsALDH (IC50 value: 33.5 ± 2.5 µM), and the mechanism of inhibition was mixed type (in between competitive and non-competitive). Binding of As to hsALDH changed the conformation of the enzyme. A static quenching mechanism was observed between the enzyme and As with a binding constant (Kb) of 9.77 × 104 M-1. There is one binding site for As on hsALDH molecule. Further, the activity of hsALDH in volunteers living in regions of higher As levels in drinking water (Bahroli and Mirganj village of Bareilly district, India), and those living in region having safe levels of As (Aligarh city, India) was determined. The As level in the saliva samples of the volunteers was determined by inductively coupled plasma mass spectroscopy (ICP-MS). Low hsALDH activity was found in volunteers living in the region of higher As levels. The activity of hsALDH and As concentration in the saliva was found to be negatively correlated (r = - 0.427, p < 0.0001). Therefore, we speculate that the high incidence of cancer cases reported in Bareilly district may be due to higher As contamination.

Immobilization of laccase on Sepharose-linked antibody support for decolourization of phenol red.

Laccases which are considered as "green tools" in biotechnology have potential to degrade toxic contaminants/synthetic dyes present in industrial effluents. The loss in activity and stability of laccases are key challenges faced in their potential industrial applications. Here, laccase from Trametes versicolor (polypore mushroom) was immobilized on Sepharose-linked antibody support to carry out the decolourization of phenol red. This support was prepared by covalent linking of anti-laccase antibodies to CNBr activated Sepharose at pH 8.5, and then laccase was immobilized on this affinity support at pH 5.0. The amount of laccase immobilized was approximately 33 mg per gram of the affinity support, giving an immobilization yield of 83.4%. The immobilized enzyme displayed an activity of 3.88 U with an effectiveness factor (η) of 0.90. Immobilization of laccase led to significant enhancement in thermal and storage stability. The immobilized enzyme retained 44% of its activity after 10 cycles of continuous use. The decolourization of phenol red dye obtained by immobilized and soluble laccase after 6 h of incubation at 50 °C was 80 and 56%, respectively. Thus, immobilization of laccase on Sepharose-linked antibody support leads to remarkable improvement in its various properties, making it more versatile for industrial applications.

Structural-Dependent N,O-Donor Imine-Appended Cu(II)/Zn(II) Complexes: Synthesis, Spectral, and in Vitro Pharmacological Assessment.

Four mononuclear bioefficient imine-based coordination complexes, [(L 1 ) 2 Cu], [(L 1 ) 2 Zn], [(L 2 )Cu(H 2 O)], and [(L 2 )Zn(H 2 O)], were synthesized using ligands [L 1 = 2-(((3-hydroxynaphthalen-2-yl)methylene)amino)-2-methylpropane-1,3-diol and L 2 = 4-(1-((1,3-dihydroxy-2-methylpropan-2-yl)imino)ethyl)benzene-1,3-diol]. The formation of the complexes was ascertained by elemental analysis, Fourier transform infrared, 1H NMR, 13C NMR, electrospray ionization-mass spectroscopy, electron paramagnetic resonance, and thermogravimetric analysis. The comparative binding propensity profiles of the above-synthesized complexes with the DNA/human serum albumin (HSA) were investigated via UV absorption, fluorescence, and Förster resonance energy-transfer studies. On the basis of extended conjugation and planarity, L 1 complexes exhibited superior bioactivity with greater calculated DNA binding constant values, (K b) 2.9444 × 103 [(L 1 ) 2 Cu] and 2.2693 × 103 [(L 1 ) 2 Zn], as compared to L 2 complexes, 1.793 × 103 [(L 2 )Cu(H 2 O)] and 9.801 × 102 [(L 2 )Zn(H 2 O)]. The competitive displacement assay of complexes was performed by means of fluorogenic dyes (EtBr and Hoechst), which corroborates the occurrence of minor groove binding because of the enhanced displacement activity with Hoechst 33258. The minor groove binding of the [(L 1 ) 2 Cu] complex is further confirmed by the molecular docking study. Moreover, the HSA study demonstrated effective static quenching of complexes with substantial K sv values. The [(L 1 ) 2 Cu] complex was found to have pronounced cleavage efficiency as evaluated from sodium dodecyl sulfate polyacrylamide gel electrophoresis electrophoresis. Furthermore, in vitro antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl and superoxide radicals further proclaimed the remarkable bioefficiency of compounds, which make them promising as active chemotherapeutic agents.

Immobilization of ß-galactosidase on tannic acid stabilized silver nanoparticles: A safer way towards its industrial application.

In this study, ß-galactosidase has been immobilized on tannic acid stabilized silver nanoparticles (AgNPs). Tannic acid is a phytochemical and it is advantageous to use it as a linker molecule for immobilization because of its antidiarrheal and antimicrobial properties, and very low toxicity. AgNPs with immobilized ß-galactosidase were characterized for particle size and catalytic properties. The AgNPs consisted of almost monodispersed particles of average diameter of ∼20 nm. ß-galactosidase immobilized on tannic acid stabilized AgNPs (83.6% Immobilization yield) exhibited good activity with a high enzyme to carrier ratio as compared to the previous reports. Immobilization did not affect the optimum pH (pH 4.5) of the enzyme, however it retained greater fraction of activity in both alkaline and acidic pH range. The immobilized enzyme exhibited greater fraction of activity at higher temperatures as compared to the soluble enzyme, and its optimum temperature increased by 5 °C. The immobilized enzyme retained almost 60% of its activity after 10th successive use. The immobilized enzyme hydrolyzed 258 and 474 µM lactose from 1% lactose and from milk lactose, respectively, whereas the soluble enzyme hydrolyzed 235 and 424 µM lactose from 1% lactose and from milk lactose, respectively. Excellent activity and stability of ß-galactosidase immobilized on AgNPs provides a cost-effective industrial application of this enzyme. ß-galactosidase immobilized on tannic acid stabilized AgNPs are free from toxicity hazards of the linker molecules. Hence, it may find constructive enzyme based applications in food technology.

Enzymes and nanoparticles: Modulation of enzymatic activity via nanoparticles.

Enzymes are biocatalysts that speed up the reactions taking place inside the cell. They are widely used in industries, scientific research and clinical diagnostics. Enzymes are specific for their substrates. They increase the rate of reaction by lowering the activation energy required to convert the substrates into the products. The catalysis by an enzyme is influenced by the nature of medium, substrate, enzyme concentration, temperature, pH, and the presence of activators and inhibitors. Nanoparticles are solid dispersion particulates of size range 10-1000 nm. They cause enhancement of particle mobility, diffusion, thermal stability, storage capacity, greater surface area and also modulate catalytic activity of the attached enzymes. Enzymes can be immobilized on nanoparticles by simple adsorption or via chemical linkages. Immobilization is a commercially applicable and a convenient method because it usually results in enhanced thermal and pH stabilities of the enzyme, lower cost of production, reusability with easy handling and separation. Primary objective of writing this review is to give an overview of the various aspects of enzymology, enzyme catalysis, enzyme immobilization and modulation of enzyme activity with special emphasis on modulation through different types of nanoparticles including their synthesis, characterization and applications.