title: Unidirectional inhibition of phosphoenolpyruvate carboxykinase from Rhodospirillum rubrum by ATP.
abstract: The kinetic and regulatory properties of partially purified phosphoenolpyruvate (PEP) carboxykinase (EC 4.1.1.3.2) from Rhodospirillum rubrum were studied. The enzyme was active with guanosine- and inosinephosphates and must thus be classified as GTP (ITP): oxaloacetate carboxylase (transphosphorylating.) In the direction of oxaloacetate-foramtion, the enzyme was strongly inhibited by ATP (Ki = 0.03 mM). ITP, UTP, CTP, and GTP were less inhibitory. The inhibition was competitive with respect to GDP or IDP, but not with respect to PEP. In the direction of PEP-synthesis, the enzyme was not inhibited, but rather activated by ATP.
mesh_terms: D000255:Adenosine Triphosphate; D004794:Enzyme Repression / Q000187:drug effects; D007700:Kinetics; D009711:Nucleotides; D010728:Phosphoenolpyruvate / Q000096:biosynthesis; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D012247:Rhodospirillum rubrum / Q000201:enzymology*
chemical_list: D009711:Nucleotides; D010728:Phosphoenolpyruvate; D000255:Adenosine Triphosphate; D010729:Phosphoenolpyruvate Carboxykinase (GTP)