title: The effect of the sesquiterpene lactones from Geigeria on glycolytic enzymes.
abstract: The effect of sesquiterpene lactones isolated from Geigeria was tested on three glycolytic enzymes. Phosphofructokinase was inhibited irreversibly by all of the sesquiterpene lactones, with ivalin(III) giving the highest extent of inhibition. Values for the kinetic constants Ki (1.3 mM) and kp (2.2 min-1) were established. Hexokinase and glyceraldehyde-3-phosphate dehydrogenase were also strongly inhibited at 1 mM and 3 mM concentrations of sesquiterpene lactones, respectively. Pre-incubation of ivalin with dithiothreitol decreased its inhibiting effect on phosphofructokinase, hexokinase and glyceraldehyde-3-phosphate dehydrogenase activities. Phosphofructokinase and hexokinase were protected against inhibition by ivalin by their respective substrates, adenosine-5'-triphosphate and glucose.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000037:antagonists & inhibitors*; D006019:Glycolysis / Q000187:drug effects*; D006593:Hexokinase / Q000037:antagonists & inhibitors*; D066298:In Vitro Techniques; D007700:Kinetics; D007783:Lactones / Q000494:pharmacology*; D010732:Phosphofructokinase-1 / Q000037:antagonists & inhibitors*; D010936:Plant Extracts / Q000494:pharmacology; D010947:Plants, Toxic; D012717:Sesquiterpenes / Q000494:pharmacology*
chemical_list: D007783:Lactones; D010936:Plant Extracts; D012717:Sesquiterpenes; C049171:ivalin; D000255:Adenosine Triphosphate; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D006593:Hexokinase; D010732:Phosphofructokinase-1; D005947:Glucose; D004229:Dithiothreitol