title: Na+, K+-dependent ATPase activity and effect of K+ on in vitro protein synthesis and NAD pyrophosphorylase in Toxoplasma gondii.
abstract: Although Na+, K+-dependent ATPase activity was barely detectable in extracellular tachyzoites of Toxoplasma gondii, Mg++-dependent ATPase was readily demonstrable. Based on this finding, the effect of K+ on in vitro protein synthesis and NAD pyrophosphorylase of T. gondii was evaluated. Addition of KCl enhanced in vitro protein synthesis. NAD pyrophosphorylase also was activated by KCl. The optimal concentration of KCl for both enzymatic reactions was 150 mM. The supernatant fluid (15,000 g, 20 min) isolated from the homogenate of purified tachyzoites of T. gondii contained more Na+ than K+. Evaluation of leakage of Na+ and K+ from purified tachyzoites suggested that Na+ leaked more than K+. These observations suggest an important role of K+ in the regulation of the metabolism of T. gondii.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D008274:Magnesium / Q000494:pharmacology; D009612:Nicotinamide-Nucleotide Adenylyltransferase / Q000378:metabolism*; D009713:Nucleotidyltransferases / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology*; D014176:Protein Biosynthesis; D012964:Sodium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014122:Toxoplasma / Q000378:metabolism*
chemical_list: D012964:Sodium; D009713:Nucleotidyltransferases; D009612:Nicotinamide-Nucleotide Adenylyltransferase; D000251:Adenosine Triphosphatases; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium; D011188:Potassium