In vitro activity and stability of pure human salivary aldehyde dehydrogenase

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.

High-Precision Viral Detection Using Electrochemical Kinetic Profiling of Aptamer-Antigen Recognition in Clinical Samples and Machine Learning

High-precision viral detection at point of need with clinical samples plays a pivotal role in the diagnosis of infectious diseases and the control of a global pandemic. However, the complexity of clinical samples that often contain very low viral concentrations makes it a huge challenge to develop simple diagnostic devices that do not require any sample processing and yet are capable of meeting performance metrics such as very high sensitivity and specificity. Herein we describe a new single-pot and single-step electrochemical method that uses real-time kinetic profiling of the interaction between a high-affinity aptamer and an antigen on a viral surface. This method generates many data points per sample, which when combined with machine learning, can deliver highly accurate test results in a short testing time. We demonstrate this concept using both SARS-CoV-2 and Influenza A viruses as model viruses with specifically engineered high-affinity aptamers. Utilizing this technique to diagnose COVID-19 with 37 real human saliva samples results in a sensitivity and specificity of both 100 % (27 true negatives and 10 true positives, with 0 false negative and 0 false positive), which showcases the superb diagnostic precision of this method.

Immobilization of GOx Enzyme on SiO2-Coated Ni-Co Ferrite Nanocomposites as Magnetic Support and Their Antimicrobial and Photocatalytic Activities

The present study used a sol-gel auto-combustion approach to make silica (SiO2)-coated Ni-Co ferrite nanocomposites that would be used as a platform for enzyme immobilization. Using glutaraldehyde as a coupling agent, glucose oxidase (GOx) was covalently immobilized on this magnetic substrate. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), and fourier transform infrared spectroscopy (FTIR) was used to determine the structural analysis and morphology of Ni-Co ferrite/SiO2 nanocomposites. FTIR spectra confirmed the binding of GOx to Ni-Co ferrite/SiO2 nanocomposites, with a loading efficiency of around 85%. At alkaline pH and higher temperature, the immobilized GOx enzyme exhibited increased catalytic activity. After 10 times of reuses, it still had 69% catalytic activity. Overall, the immobilized GOx displayed higher operational stability than the free enzyme under severe circumstances and was easily recovered by magnetic separation. With increased doping concentration of the nanocomposites, the photocatalytic activity was assessed using a degradation process in the presence of methylene blue dye under UV light irradiation, which revealed that the surface area of the nanocomposites with increased doping concentration played a significant role in improving photocatalytic activity. The antibacterial activity of Ni-Co ferrite/SiO2 nanocomposites was assessed using the agar well diffusion method against Escherichia coli, a gram-negative bacteria (ATCC 25922). Consequently, it was revealed that doping of Ni2+ and Co2+ in Fe2O4/SiO2 nanocomposites at varied concentrations improved their antibacterial properties.

Correlation between the Activity of Aldehyde Dehydrogenase and Oxidative Stress Markers in the Saliva of Diabetic Patients

BACKGROUND

Reactive aldehydes are involved in diseases associated with oxidative stress, including diabetes. Human salivary aldehyde dehydrogenase (hsALDH) presumably protects us from many toxic ingredient/contaminant aldehydes present in food.

OBJECTIVE

This study aimed to probe the activity of hsALDH in patients with diabetes and than to correlate it with various oxidative stress markers in the saliva.

METHODS

The saliva samples were collected from total 161 diabetic patients from Rajiv Gandhi Centre for Diabetes, Jawaharlal Nehru Medical College (JNMC), AMU, Aligarh, (India). HsALDH activity and markers of oxidative stress [8-hydroxydeoxyguanosine (8-OHDG), malondialdehyde (MDA) and advanced glycation end products (AGEs)] were measured in the saliva samples.

RESULTS

Patients with early stage of diabetes had higher activity of hsALDH when compared with the control group. As the history of diabetes increases, the activity of the enzyme decreases and also higher oxidative stress markers (8-OHDG, MDA and AGEs) are detected in the saliva samples. Negative significant correlation between hsALDH activity and oxidative stress markers were observed (p <0.0001).

CONCLUSION

The activity of hsALDH increases in early stages of diabetes most probably to counter the increased oxidative stress associated with diabetes. However, in later stages of diabetes, the activity of the enzyme decreases, possibly due to its inactivation resulting from glycation.

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 (K_b) 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.

Citral Inhibition of Human Salivary Aldehyde Dehydrogenase

Human salivary aldehyde dehydrogenase (hsALDH) protects us from the toxic effect of aldehydes. It has both diagnostic and therapeutic importance. Citral possesses many biological and pharmacological properties. The aim of this work was to investigate the inhibitory effect and the mechanism of inhibition of citral on hsALDH. Citral inhibits the dehydrogenase activity of hsALDH. It decreased the substrate affinity and to a lesser extent, the catalytic efficiency of hsALDH. Citral showed linear mixed-type inhibition with a higher tendency of competitive behavior with little, but significant, non-competitive inhibition. The nucleophilicity of active site Cys residue is not a significant contributing factor in the inhibition process. Citral shows uncompetitive inhibition towards the co-enzyme (NAD⁺). α-helix and β-sheet content of the enzyme were changed in presence of citral. Biophysical studies showed that citral quenches the intrinsic fluorescence of hsALDH in a static manner by forming complex with the enzyme. Molecular docking study showed that both the isomers of citral bind to the catalytic site of hsALDH interacting with few evolutionary preserved amino acid residues through multiple non-covalent interactions. Ligand efficiency metrics values indicate that citral is an efficient ligand for the enzyme in terms of its physicochemical and pharmacokinetic properties.

Enhancement in the Catalytic Activity of Human Salivary Aldehyde Dehydrogenase by Alliin from Garlic: Implications in Aldehyde Toxicity and Oral Health

BACKGROUND

Lower human salivary aldehyde dehydrogenase (hsALDH) activity increases the risk of aldehyde mediated pathogenesis including oral cancer. Alliin, the bioactive compound of garlic, exhibits many beneficial health effects.

OBJECTIVE

To study the effect of alliin on hsALDH activity.

METHODS

Enzyme kinetics was performed to study the effect of alliin on the activity of hsALDH. Different biophysical techniques were employed for structural and binding studies. Docking analysis was done to predict the binding region and the type of binding forces.

RESULTS

Alliin enhanced the dehydrogenase activity of the enzyme. It slightly reduced the Km and significantly enhanced the Vmax value. At 1 µM alliin concentration, the initial reaction rate increased by about two times. Further, it enhanced the hsALDH esterase activity. Biophysical studies indicated a strong complex formation between the enzyme and alliin (binding constant, Kb: 2.35 ± 0.14 x 103 M-1). It changes the secondary structure of hsALDH. Molecular docking study indicated that alliin interacts to the enzyme near the substrate binding region involving some active site residues that are evolutionary conserved. There was a slight increase in the nucleophilicity of active site cysteine in the presence of alliin. Ligand efficiency metrics values indicate that alliin is an efficient ligand for the enzyme.

CONCLUSION

Alliin activates the catalytic activity of the enzyme. Hence, consumption of alliincontaining garlic preparations or alliin supplements and use of alliin in pure form may lower aldehyde related pathogenesis including oral carcinogenesis.

Thymoquinone binds and activates human salivary aldehyde dehydrogenase: Potential therapy for the mitigation of aldehyde toxicity and maintenance of oral health

Human salivary aldehyde dehydrogenase (hsALDH) is a very important anti-oxidant enzyme present in the saliva. It is involved in the detoxification of toxic aldehydes and maintenance of oral health. Reduced level of hsALDH activity is a risk factor for oral cancer development. Thymoquinone (TQ) has many pharmacological activities and health benefits. This study aimed to examine the activation of hsALDH by TQ. The effect of TQ on the activity and kinetics of hsALDH was studied. The binding of TQ with the enzyme was examined by different biophysical methods and molecular docking analysis. TQ enhanced the dehydrogenase activity of crude and purified hsALDH by 3.2 and 2.9 fold, respectively. The K_m of the purified enzyme decreased and the V_max increased. The esterase activity also increased by 1.2 fold. No significant change in the nucleophilicity of the catalytic cysteine residue was observed. TQ forms a strong complex with hsALDH without altering the secondary structures of the enzyme. It fits in the active site of ALDH3A1 close to Cys 243 and the other highly conserved amino acid residues which lead to enhancement of substrate binding affinity and catalytic efficiency of the enzyme. TQ is expected to give better protection from toxic aldehydes in the oral cavity and to reduce the risk of oral cancer development through the activation of hsALDH. Therefore, the addition of TQ in the diet and other oral formulations is expected to be beneficial for health.

Monitoring thermal and chemical unfolding of Brugia malayi calreticulin using fluorescence and Circular Dichroism spectroscopy

Calreticulin of Brugia malayi (BmCRT) play very important role in host-parasite interaction. In previous study it was found that BmCRT is responsible for prevention of host classical complement pathway activation via its interaction with first component C1q of the human host. Therefore, BmCRT is an essential protein for parasite survival and an important drug target to fend filariasis. In the present study, we have carried out a systamatic biophysical characterization of BmCRT protein. Unfolding of BmCRT was found to be non-cooperative two-state process in the presence of both denaturant GdmCl and urea. The results also illustrated that protein lost its 50% activity at 1.5M GdmCl and 3M Urea. Partially unfolded and molten-globule like intermediate state was observed at 0.8 to 1.2M GdmCl while Urea unfolding showed intermediate state at 1.2 to 1.6M. Unfolding pathway monitored with the help of apolar quencher, favor above observations. All of these findings support the presence of detectable intermediate state during unfolding pathway of BmCRT. Furthermore, this study indicates that BmCRT is more stable toward temperature (Tm=65°C), pH and trypsin digestion. These differences in properties as compared to host can be fruitfully utilized for synthesis of compounds effective against the parasite.