Purification and biochemical characterization of glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and glutathione reductase from rat lung and inhibition effects of some antibiotics

The Effects of Sodium Tetraborate against Lead Toxicity in Rats: The Behavior of Some Metabolic Enzymes

This study was planned to research the in vivo effects of lead (Pb) ions and sodium tetraborate (Na2B4O7) on G6PD and 6PGD, which are some of the enzymes of the pentose phosphate pathway, which carries vital importance for metabolism, and GR and GST, which are glutathione metabolism enzymes, and the in vitro effects of the same agents on the 6PGD enzyme. According to the in vivo analysis results, in comparison to the control group, the rat liver G6PD (p < 0.05), and 6PGD (p < 0.01) enzyme activities in the Na2B4O7 group were significantly lower. In addition, GR and GST enzyme activities were insignificantly lower in the Na2B4O7 group compared to the control group (p > 0.05). The Pb group had lower G6PD and 6PGD enzyme activity levels and higher GR and GST enzyme activity levels compared to the control group, while these changes did not reach statistical significance (p > 0.05). In the in vitro analyses of the effects of Pb ions on the 6PGD enzyme that was purified out of rat liver with the 2',5'-ADP-Sepharose 4B affinity chromatography method, it was determined that Pb ions (200-1200 μM) increased the rat liver 6PGD enzyme activity levels by 33%. On the other hand Na2B4O7 was not significantly effective on 6PGD activity. These results will also contribute to future studies in understanding the physiopathology of the states triggered by Pb ions and sodium tetraborate (Na2B4O7).

Ameliorative effects of astaxanthin against copper(II) ion-induced alteration of pentose phosphate pathway and antioxidant system enzymes in rats

Copper (Cu) is one of the toxic elements that cause environmental pollution. As a result of excessive accumulation of copper in the organism, it causes damage in various organs and tissues and hemolysis in erythrocytes. Astaxanthin (ATX) is a pigment belonging to the xanthophyll family, which is an oxygenated derivative of carotenoids. Thanks to its powerful antioxidant properties, ATX has an extraordinary potential to protect the organism against various diseases, especially cancer. The main objective of this study was to investigate the toxic effect of copper ions on the glucose 6-phosphate dehydrogenase (G6PD), 6-phospho-gluconate dehydrogenase (6PGD), glutathione reductase (GR), glutathione S-transferase (GST), and thioredoxin reductase (TrxR) enzymes and the role of astaxanthin in reducing this effect. In in vivo study, Wistar Albino male rats (n=28) were randomly divided into 4 groups: the control group, copper (Cu2+) group, astaxanthin (ATX) group, and copper + astaxanthin (Cu2++ATX) group. The results show that G6PD enzyme activity in Cu2+ group was strongly inhibited (p ˂ 0.05), while in other groups, there were no significant effects compared to the control group (p ⩾ 0.05). 6PGD enzyme activity was significantly reduced in Cu2+ group compared to that in the control group (p ˂ 0.05), and GR enzyme activity was lower in Cu2+ group compared to that in the control group (p ˂ 0.05). Similarly, when GST enzyme activity was evaluated, a strong decrease was observed in the Cu2+ group compared to that in the control group (p ˂ 0.05), while the enzyme activity in the Cu2++ATX group approached the control group (p ⩾ 0.05). When TrxR enzyme activity level was examined, a statistically significant decrease was observed in the Cu2+ and Cu2++ATX groups (p ˂ 0.05), and the enzyme activity in the ATX group was found to be close to that in the control group. When in vitro results were evaluated, it was observed that copper ions inhibited G6PD enzyme purified from rat erythrocyte tissues with IC50=1.90 μM value and Ki = 0.97 μM ± 0.082 value and the inhibition was non-competitive. From the results, it can be concluded that Cu2+ ions have an inhibitory effect on rat erythrocyte pentose phosphate pathway and antioxidant system enzymes both in vivo and in vitro, and astaxanthin reduces this effect.

Biochemical and structural insights into 6-phosphogluconate dehydrogenase from Leishmania donovani

6-phosphogluconate dehydrogenase (6PGDH) participates in pentose phosphate pathway of glucose metabolism by catalyzing oxidative decarboxylation of 6-phsophogluconate (6PG) and its absence has been lethal for several eukaryotes. Despite being a validated drug target in many organisms like Plasmodium, the enzyme has not been explored in leishmanial parasites. In the present study, 6PGDH of Leishmania donovani (Ld6PGDH) is cloned and purified followed by its characterization using biochemical and structural approaches. Ld6PGDH lacks the glycine-serine-rich sequence at its C-terminal that is present in other eukaryotes including humans. Leishmanial 6PGDH possesses more affinity for substrate (6PG) and cofactor (NADP) in comparison to that of human. The enzymatic activity is inhibited by gentamicin and cefuroxime through competitive mode with functioning more potently towards leishmanial 6PGDH than its human counterpart. CD analysis has shown higher α-helical content in the secondary structure of Ld6PGDH, while fluorescence studies revealed that tryptophan residues are not completely accessible to solvent environment. The three-dimensional structure was generated through homology modelling and docked with substrate and cofactor. The docking studies demonstrated two separate binding pockets for 6PG and NADP with higher affinity for the cofactor binding, and Asn105 is interacting with substrate as well as the cofactor. Additionally, MD simulation has shown complexes of Ld6PGDH with 6PG and NADP to be more stable than its apo form. Altogether, the present study might provide the foundation to investigate this enzyme as potential target against leishmaniasis. KEY POINTS: • Ld6PGDH enzymatic activity is competitively inhibited by gentamicin and cefuroxime. • It displays more helical contents and all structural characteristics of 6PGDH family. • Interaction studies demonstrate higher affinity of cofactor than substrate for Ld6PGDH.

The effects of chrysin and naringin on cyclophosphamide-induced erythrocyte damage in rats: biochemical evaluation of some enzyme activities in vivo and in vitro

In recent years, there have been efforts to develop therapeutic agents that target metabolic enzyme systems in addition to existing treatment in possible cancer treatments. Cyclophosphamide (CYP) is an anticancer drug commonly used in various cancer treatments. Chrysin (CH) and naringin (NR) are natural flavonoids that possess many medicinal and pharmacological properties. In the present study, we aimed to investigate the effect of CH and NR against CYP-induced toxicity on some metabolic enzyme activities. For this purpose, 56 male rats were randomly divided into 8 groups in our in vivo study. The rats were pretreated with CH (25 and 50 mg/kg bw) and NR (50 and 100 mg/kg bw) for 7 days before administering a single dose of CYP (200 mg/kg bw) on the seventh day. According to the in vivo results of our study, it was observed that CH and NR regulated abnormal changes in CYP-induced enzyme activities. In addition, our in vitro study, G6PD enzyme was purified from rat erythrocyte using affinity chromatography. The effects of CH, NR, and CYP were investigated on the purified enzyme. It was determined that CH increased the enzyme activity, CYP ineffective on the enzyme activity, whereas NR inhibited the enzyme activity noncompetitively. Graphical abstract.

The Pentose Phosphate Pathway Dynamics in Cancer and Its Dependency on Intracellular pH

The Pentose Phosphate Pathway (PPP) is one of the key metabolic pathways occurring in living cells to produce energy and maintain cellular homeostasis. Cancer cells have higher cytoplasmic utilization of glucose (glycolysis), even in the presence of oxygen; this is known as the "Warburg Effect". However, cytoplasmic glucose utilization can also occur in cancer through the PPP. This pathway contributes to cancer cells by operating in many different ways: (i) as a defense mechanism via the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) to prevent apoptosis, (ii) as a provision for the maintenance of energy by intermediate glycolysis, (iii) by increasing genomic material to the cellular pool of nucleic acid bases, (iv) by promoting survival through increasing glycolysis, and so increasing acid production, and (v) by inducing cellular proliferation by the synthesis of nucleic acid, fatty acid, and amino acid. Each step of the PPP can be upregulated in some types of cancer but not in others. An interesting aspect of this metabolic pathway is the shared regulation of the glycolytic and PPP pathways by intracellular pH (pHi). Indeed, as with glycolysis, the optimum activity of the enzymes driving the PPP occurs at an alkaline pHi, which is compatible with the cytoplasmic pH of cancer cells. Here, we outline each step of the PPP and discuss its possible correlation with cancer.

Inhibition effects of some antidepressant drugs on pentose phosphate pathway enzymes

The glucose metabolism in the pentose cycle is essential to the source of NADPH. Deficiency of these enzymes have been linked to depression and psychotic disorders. Depression is an increasingly prevalent mental disorder which may cause loss of labor. Antidepressant drugs are commonly employed in treatments of mood disorders and anxiety treatment. The purpose of this study is to investigate the effects of aripiprazole, mirtazapine, risperidone, escitalopram and haloperidol on the activity of 6-phosphogluconate dehydrogenase (6PGD) and glucose-6-phosphate dehydrogenase (G6PD) enzymes purified from human erythrocytes. It was found that aripiprazole, mirtazapine, risperidone, escitalopram and haloperidol show effective inhibitor properties on purified G6PD and 6PGD enzymes. The IC₅₀ values of these drugs were found in the range of 26.34 μM-5.78 mM for 6PGD and 16.26 μM-3.85 mM for G6PD. The K_i values of the drugs were found in the range of 30.21 ± 4.31 μM-4.51 ± 1.83 mM for 6PGD and 14.12 ± 3.48 μM-4.98 ± 1.14 mM for G6PD. Usage of drugs with significant biological effects may be a hazard in some conditions.

In vitro and in vivo effects of iron on the expression and activity of glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and glutathione reductase in rat spleen

Iron is an indispensable element for vital activities in almost all living organisms. It is also a cofactor for many proteins, enzymes, and other essential complex biochemical processes. Therefore, iron trafficking is firmly regulated by Hepcidin (Hamp), which is regarded as the marker for iron accumulation. The disruption of iron homeostasis leads to oxidative stress that causes various human diseases, but this mechanism is still unclear. The aim of this study is to provide a better in vivo and in vitro understanding of how long-term iron overload affects the gene expression and activities of some antioxidant enzymes, such as glucose 6-phosphate dehydrogenase (G6PD), 6-phosphogluconate dehydrogenase (6PGD), and glutathione reductase (GR) in the spleen. The findings of this study show that iron overload reduces the gene expression of G6pd, 6pgd, and Gr, but its actual effect was on the protein level.

The effect of astaxanthin and cadmium on rat erythrocyte G6PD, 6PGD, GR, and TrxR enzymes activities in vivo and on rat erythrocyte 6PGD enzyme activity in vitro

In this study, the effects of astaxanthin (AST) that belongs to carotenoid family and cadmium (Cd), which is an important heavy metal, on rat erythrocyte G6PD, 6PGD, GR, and TrxR enzyme activities in vivo and on rat erythrocyte 6PGD enzyme activity in vitro were studied. In in vitro studies, 6PGD enzyme was purified from rat erythrocytes with 2',5'-ADP Sepharose4B affinity chromatography. Results showed inhibition of enzyme by Cd at IC₅₀ ; 346.5 μM value and increase of 6PGD enzyme activity by AST. In vivo studies showed an increase in G6PD, 6PGD, and GR enzyme activities (P ˃ 0.05) and no chance in TrxR enzyme activity by AST. Cd ion inhibited G6PD, 6PGD, and GR enzyme activities (P ˂ 0.05) and also decreased TrxR enzyme activity (P ˃ 0.05). AST + Cd group G6PD enzyme activity was statistically low compared with control group (P ˂ 0.05). 6PGD and TrxR enzyme activities decreased without statistical significance (P ˃ 0.05); however, GR enzyme activity increased statistically significantly (P ˂ 0.05).