Accumulation of oxidative damage has been implicated to be a major causative factor in the decline in physiological functions that occur during the aging process. The mitochondrial respiratory chain is a powerful so urce of reactive oxygen species (ROS), considered as the pathogen ic agent of many diseases and aging. L-malate, a tricarboxylic acid cycle intermediate, plays an important role in transporting NADH from cytosol to mitochondria for energy production. Previous studies in our laboratory reported L-malate as a free radical scavenger in aged rats. In the present study we focused on the effect of L-malate on the activities of electron transport chain in young and aged rats. We found that mitochondrial membrane potential (MMP) and the activities of succinate dehydrogenase, NADH-cytochrome c oxidoreductase and cytochrome c oxidase in liver of aged rats were significantly decreased when compared to young control rats. Supplementation of L-malate to aged rats for 30 days slightly increased MMP and improved the activities of NADH-dehydrogenase, NADH-cytochrome c oxidoreductase and cytochrome c oxidase in liver of aged rats when compared with aged control rats. In young rats, L-malate administration increased only the activity of NADH-dehydrogenase. Our result suggested that L-malate could improve the activities of electron transport chain enzymes in aged rats., J.-L. Wu ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
L-malate, a tricarboxylic acid cycle (TCA ) intermediate, plays an important role in transporting NADH from cytosol to mitochondria for energy production and may be involved in the beneficial effects of improving physical stamina. In the present study, we investigated the effects of L-malate on the performance of forced swimming time and blood biochemical parameters related to fatigue – blood urea nitrogen (BUN), glucose (Glc), creatine kinase (CK) , total protein (TP) and lactic acid (LA). To investigate the effects of L-malate on the malate-aspartate shuttle and energy metabolism in mice, the activities of enzymes related to the malate-aspartate shuttle were measured. L-malate was orally administered to mice continuously for 30 days using a feeding atraumatic needle. The swimming time was increased by 26.1 % and 28.5 %, respectively, in the 0.210 g/kg and 0.630 g/kg L-malate-treated group compared with the control group. There were no differences in the concentrations of Glc, BUN and TP between the L-malate-treated groups and the control groups. However, the levels of CK were significantly decreased in the L-malate-treated groups. The results predict a potential benefit of L-malate for improving physical stamina and minimizing muscle damage during swimming exercise. The activities of cytosolic and mitochondrial malate dehydrogenase were significantly elevated in the L-malate-treated group compared with the control group. These enzymatic activities may be useful indicators for evaluating changes affecting the malate-aspartate shuttle and energy metabolism in the liver of mice., J. L. Wu, Q. P. Wu, J. M. Huang, R. Chen, M. Cai, J. B. Tan., and Obsahuje bibliografii a bibliografické odkazy
The intracellular levels of antioxidant and free radical scavenging enzymes are gradually altered during the aging process. An age-dependent increase of oxidative stress occurring throughout the lifetime is hypothesized to be the major cause of aging. The current study examined the effects of L-malate on oxidative stress and antioxidative defenses in the liver and heart of aged rats. Sprague-Dawley male rats were randomly divided into four groups, each group consisting of 6 animals. Group Ia and Group IIa were young and aged control rats. Group Ib and Group IIb were young and aged rats treated with L-malate (210 mg/kg body weight per day). L-malate was orally administrated via intragastric canula for 30 days, then the rats were sacrificed and the liver and heart were removed to determine the oxidant production, lipid peroxidation and antioxidative defenses of young and aged rats. Dietary L-malate reduced the accumulation of reactive oxygen species (ROS) and significantly decreased the level of lipid peroxidation in the liver and heart of the aged rats. Accordingly, L-malate was found to enhance the antioxidative defense system with an increased activity of antioxidant enzymes, such as superoxide dismutase (SOD) and glutathione peroxidase (GPx) and increased glutathione (GSH) levels in the liver of aged rats, a phenomenon not observed in the heart of aged rats. Our data indicate that oxidative stress was reversed and the antioxidative defense system was strengthened by dietary supplementation with L-malate., J.-L. Wu, Q.-P. Wu, X.-F. Yang, M.-K. Wei, J.-M. Zhang, Q. Huang, X.-Y. Zhou., and Obsahuje bibliografii a bibliografické odkazy
Feeding K+ or Na+ nitrate salts in vivo enhanced the activity of phosphoenolpyruvate carboxylase (PEPC) in the leaf extracts of Alternanthera pungens (C4 plant) and A. sessilis (C3 species). The increase was more pronounced in A. pungens than in A. sessilis. Chloride salts increased the PEPC activity only marginally. However, the sulfate salts were either not effective or inhibitory. Feeding nitrate modulated the regulatory properties of PEPC in A. pungens, resulting in increased KI (malate) and decreased KA (glucose-6-P). The sensitivity of PEPC to malate, which gives a measure of phosphorylation status of the enzyme, indicated that feeding leaves with NO3- enhanced the phosphorylation status of the enzyme. The reduction in PEPC activity due to cycloheximide treatment suggested that increased synthesis of PEPC protein kinase may be one of the reasons for the enhancement in PEPC activity, after the nitrate feeding. We suggest that nitrate salts could be used as a tool to modulate and analyze the properties of PEPC in C3 and C4 plants. and A. V. Rajagopalan, R. M. Agarwal, A. S. Raghavendra.
A traditional method is reported for purification of phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) from leaves of Amaranthus hypochondriacus L. with a high yield of 50 %, 135-fold purification, and specific activity of 900 mmol kg-1(protein) s-1. PEPC was purified from light-adapted leaves of A. hypochondriacus, involving 40-60 % ammonium sulphate fractionation, followed by chromatography on columns of DEAE-Sepharose, hydroxylapatite (HAP), and Seralose 6-B. The enzyme appeared as a single band on 10 % SDS-PAGE, with a molecular mass of about 100 kDa. Kinetic studies with purified enzyme confirmed the PEPC to be the light-form of the enzyme. Glycerol generally increased the stability of PEPC. The stability and storage of the purified enzyme was studied at temperatures of 4 °C, -20 °C, and liquid nitrogen. PEPC maintained its activity for up to 3 months upon storage with 50 % (v/v) glycerol in liquid nitrogen. and J. Gayathri, K. Parvathi, A. S. Raghavendra.