title: [Kinetic mechanisms of enzyme activity of the thromboxane synthetase system. Thromboxane synthetase of human platelets].
abstract: Partially purified preparations of prostaglandin endoperoxide-synthetase (PGH-synthetase) and thromboxane synthetase (PGH-convertase) were obtained from human platelets by ion exchange chromatography. The kinetics of prostaglandin H2 enzymatic conversion was studied in the presence of thromboxane synthetase from human platelets. It was found that prostaglandin H2 conversion into both thromboxane A2 and malonic dialdehyde is a catalytic process, i. e., its rate increases as the protein concentration rises. The linear dependence of the enzymatic reaction velocity on substrate concentration at a prostaglandin H2 concentrations below 10-15 microM was demonstrated. PGH-synthetase and PGH-convertase from human platelets exhibit similar enzymatic activity dependence on pH and temperature, PGH-convertase being more thermostable.
mesh_terms: D001792:Blood Platelets / Q000201:enzymology*; D002852:Chromatography, Ion Exchange; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008315:Malondialdehyde / Q000097:blood; D010088:Oxidoreductases / Q000097:blood*; D011449:Prostaglandin Endoperoxides / Q000097:blood*; D011450:Prostaglandin Endoperoxides, Synthetic / Q000097:blood*; D044262:Prostaglandin H2; D011451:Prostaglandin-Endoperoxide Synthases / Q000097:blood*; D011463:Prostaglandins H / Q000097:blood*; D013696:Temperature; D013928:Thromboxane A2 / Q000097:blood; D013930:Thromboxane-A Synthase / Q000097:blood*
chemical_list: D011449:Prostaglandin Endoperoxides; D011450:Prostaglandin Endoperoxides, Synthetic; D011463:Prostaglandins H; D044262:Prostaglandin H2; D008315:Malondialdehyde; D013928:Thromboxane A2; D010088:Oxidoreductases; D011451:Prostaglandin-Endoperoxide Synthases; D013930:Thromboxane-A Synthase
vernacular_title: Kineticheskie zakonomernosti deĭstviia fermentov tromboksansinteziruiushcheĭ sistemy. Tromboksansintetaza trombotsitov cheloveka.