Substrate trapping experiments with P-enolpyruvate carboxykinase from rat and chickel liver

Conference · Fri May 01 04:00:00 EDT 1987 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:6416143

Satoh, Y; Schramm, V L

Equilibrium mixtures of P-enolpyruvate carboxykinase (PEPCK) and Mg( -TSP)GTP were mixed with excess oxalacetate and unlabeled MgGTP to establish the fraction of bound GTP which is commited to product formation. At saturating oxalacetate all enzyme-bound ( -TSP)GTP was converted to ( -TSP)GDP, thus the rate of catalysis is much greater than the dissociation of the PEPCK x MgGTP complex. The concentration of oxalacetate which caused half of the bound GTP to be trapped was 10-20 M. Control experiments established that no significant conversion of GTP GDP occurred in the absence of oxalacetate and no evidence was found for a covalent enzyme-phosphoryl complex. Similar results were obtained with both rat and chicken liver PEPCK's. The presence of MnS (in addition to MgS ) or the presence of KHCO3 had no effect on the GTP trapping efficiency. These experiments confirm kinetic studies which indicated that catalysis is not the slow step for the reaction catalyzed by PEPCK and establish that MgGTP binds in the proper catalytic orientation in the absence of oxalacetate, MnS or HCO3 .

• Research Organization: Temple Univ. School of Medicine, Philadelphia, PA
• OSTI ID: 6416143
• Report Number(s): CONF-870644-
• Conference Information: Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Journal Volume: 46:6
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH METAL COMPOUNDS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIRDS
BODY
CHICKENS
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
ENZYMES
FOWL
GLANDS
GUANYLIC ACID
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
LIVER
MAGNESIUM COMPOUNDS
MAMMALS
MANGANESE COMPOUNDS
NUCLEI
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANS
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
PHOSPHORUS-GROUP TRANSFERASES
PHOSPHOTRANSFERASES
RADIOISOTOPES
RATS
REACTION KINETICS
RODENTS
SUBSTRATES
TRACER TECHNIQUES
TRANSFERASES
TRANSITION ELEMENT COMPOUNDS
VERTEBRATES