title: Differential kinetics at PK/PEPCK branch point in the cestode, Raillietina echinobothrida.
abstract: Pyruvate kinase (PK; EC 2.7.1.40) and phosphoenolpyruvate carboxykinase (PEPCK; EC 4.1.1.32) are essential regulatory enzymes of glucose oxidation in helminths, the PK/PEPCK branch point being the first divergent step between carbohydrate catabolism of the parasites and their hosts. Recently, PEPCK from the cestode parasite, Raillietina echinobothrida, has been purified and characterized. In order to find out the differential kinetics, if any, at PK/PEPCK branch point in the parasite, in this study, we purified and characterized the parasite PK and compared it with the parasite PEPCK. The purified PK displayed standard Michaelis-Menten kinetics with Kmapp of 77.8 µM for its substrate PEP, whereas the Kmapp was 46.9 µM for PEPCK. PEP exhibited differential kinetics at PK/PEPCK branch point of the parasite and behaved as a homotropic effector for PEPCK, but not for PK. The inhibitory constant (Ki) for genistein and daidzein (phytochemicals from Flemingia vestita) was determined and discussed. From these results, we hypothesize that PK/PEPCK branch point is a probable site for anthelmintic action.
authors: Department of Zoology, North-Eastern Hill University, Shillong 793022, India.
authors: Bidyadhar
authors: B
authors: Das
authors: Department of Zoology, North-Eastern Hill University, Shillong 793022, India.
authors: Ramnath
authors: Department of Zoology, North-Eastern Hill University, Shillong 793022, India.
authors: Asim Kumar
authors: AK
authors: Dutta
authors: Department of Zoology, North-Eastern Hill University, Shillong 793022, India. Electronic address: tandonveena@gmail.com.
authors: Veena
authors: V
authors: Tandon
mesh_terms: D000818:Animals; D000923:Anticestodal Agents / Q000737:chemistry*; D002589:Cestoda / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000737:chemistry*; D007887:Fabaceae / Q000737:chemistry*; D019833:Genistein / Q000737:chemistry; D007529:Isoflavones / Q000737:chemistry; D007700:Kinetics; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000302:isolation & purification; D010936:Plant Extracts / Q000737:chemistry*; D011770:Pyruvate Kinase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D000923:Anticestodal Agents; D004791:Enzyme Inhibitors; D007529:Isoflavones; D010936:Plant Extracts; C004742:daidzein; D019833:Genistein; D011770:Pyruvate Kinase; D019764:Phosphoenolpyruvate Carboxykinase (ATP)
keywords: Cestode; Daidzein; Flemingia vestita; Genistein; PK/PEPCK branch point; Raillietina echinobothrida