Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.1.1.32 (phosphoenolpyruvate carboxykinase)
 4,204 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The degradation of glucose by Trypanosoma cruzi leads to the excretion of succinate. Malate dehydrogenase (MDH) participates in this process by reducing to malate the oxaloacetate synthesized by the glycosomal enzyme, phosphoenolpyruvate carboxykinase. The best coupling for these two sequential reactions would be attained if both enzymes were placed in the same subcellular compartment. The intracellular distribution of the MDH activity in epimastigotes of T. cruzi was studied by two methods. Selective disruption of cellular membranes with increasing concentrations of digitonin, indicated that trypanosomal MDH is particulate. Isopycnic centrifugation in a sucrose gradient of a large granule fraction, obtained by grinding the cells with silicon carbide, showed the presence of two MDH activities: one banding together with the glycosomal marker phosphoenolpyruvate carboxykinase, the other with the mitochondrial marker citrate synthase. Isoelectrofocusing of cell-free extracts led to the separation of two enzyme forms, with pI values of about 3.5 (MDHa) and 9.4 (MDHb). These forms had similar molecular weights (approx. 60 000) and apparent Km values, but showed a small but consistent difference in their pH optima (9.23 for MDHa and 9.05 for MDHb), and in their activation by inorganic phosphate (apparent Ka values of 33 mM and 87 mM, for MDHa and MDHb, respectively). Determination of the pH optima of the enzyme forms separated by isopycnic centrifugation suggests that the glycosomal enzyme form is MDHa, and the mitochondrial one is MDHb.
 ...
PMID:Glycosomal and mitochondrial malate dehydrogenases in epimastigotes of Trypanosoma cruzi. 637 51

Particulate fractions obtained from Trypanosoma cruzi and Crithidia fasciculata by different procedures were subjected to isopycnic centrifugation in sucrose gradients, in order to determine the subcellular localization of phosphoenolpyruvate carboxykinase (PEPCK) in both organisms, and of malic enzyme (ME) I in T. cruzi. The more clear-cut results were obtained with T. cruzi by breaking the cells by grinding in a mortar with silicon carbide and using a gradient from 0.4 to 2.0 M sucrose, whereas with C. fasciculata, the best procedure was disruption of the cells by digitonin treatment and potter homogenization and use of a gradient from 1.1 to 2.0 M sucrose. PEPCK banded together with the glycosomal marker hexokinase in both organisms; there was a clear separation from the mitochondrial markers, oligomycin-sensitive Mg2+-APTase and citrate synthase. PEPCK showed a latency of 24% in the enriched 'glycosoma' fraction of T. cruzi. ME I from T. cruzi, on the other hand, banded together with the mitochondrial markers. These results indicate that PEPCK and ME are present in different subcellular compartments, a fact significant for the prevention of a futile cycle between C4-dicarboxylic acids and C3-monocarboxylic acids, which might take place if both enzymes functioned in the same compartment.
 ...
PMID:Subcellular localization of phosphoenolpyruvate carboxykinase in the trypanosomatids Trypanosoma cruzi and Crithidia fasciculata. 675 7

Silicon (Si) fertilization improves crop cultivation and is commonly added in the form of soluble silicates. However, most natural plant-available Si originates from plant formed amorphous SiO2 particles, phytoliths, similar to SiO2-nanoparticles (SiNP). In this work we, therefore, compared the effect by sodium silicate and that of SiNP on Si accumulation, activity of antioxidative stress enzymes catalase, peroxidase, superoxide dismutase, lignification of xylem cell walls and activity of phenylalanine ammonia-lyase (PAL) as well as expression of genes for the putative silicon transporter (PST), defensive (Tfgd 1) and phosphoenolpyruvate carboxykinase (PEPCK) and protein in fenugreek (Trigonella foenum-graecum L.) grown in hydroponics. The results showed that Si was taken up from both silicate and SiNP treatments and increasing sodium silicate addition increased the translocation of Si to the shoot, while this was not shown with increasing SiNP addition. The silicon transporter PST was upregulated at a greater level when sodium silicate was added compared with SiNP addition. There were no differences in effects between sodium silicate and SiNP treatments on the other parameters measured. Both treatments increased the uptake and accumulation of Si, xylem cell wall lignification, cell wall thickness, PAL activity and protein concentration in seedlings, while there was no effect on antioxidative enzyme activity. Tfgd 1 expression was strongly downregulated in leaves at Si addition. The similarity in effects by silicate and SiNP would be due to that SiNP releases silicate, which may be taken up, shown by a decrease in SiNP particle size with time in the medium.
 ...
PMID:Comparison of silicon nanoparticles and silicate treatments in fenugreek. 2830 Jul 29