Alternate substrates and isotope effects as a probe of the malic enzyme reaction

Thesis/Dissertation · Fri Jan 01 00:00:00 EST 1988

OSTI ID:5222888

Gavva, S R

Dissociation constants for alternative dinucleotide substrates and competitive inhibitors suggest that the dinucleotide binding site of the Ascaris suum NAD-malic enzyme is hydrophobic in the vicinity of the nicotinamide ring. Changes in the divalent metal ion activator from Mg{sup 2+} to Mn{sup 2+} or Cd{sup 2+} results in a decrease in the dinucleotide affinity and an increase in the affinity for malate. Primary deuterium and {sup 13}C isotope effects obtained with the different metal ions suggest either a change in the transition state structure for the hydride transfer or decarboxylation steps or both. Deuterium isotope effects are finite whether reactants are maintained at saturating or limiting concentrations with all the metal ions and dinucleotide substrates used. For the native enzyme, primary deuterium isotope effects increase with a concomitant decrease in the {sup 13}C effects when NAD is replaced by an alternate dinucleotide substrate different in redox potential.

• Research Organization: University of North Texas, Denton, TX (USA)
• OSTI ID: 5222888
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
59 BASIC BIOLOGICAL SCIENCES
CADMIUM COMPOUNDS
BIOLOGICAL EFFECTS
DEUTERIUM
ISOTOPE EFFECTS
ENZYMES
BIOCHEMICAL REACTION KINETICS
MAGNESIUM COMPOUNDS
MALIC ACID
METABOLISM
MANGANESE COMPOUNDS
AFFINITY
ASCARIS
CARBON 13
MOLECULAR STRUCTURE
NAD
NUCLEOTIDES
RECEPTORS
SUBSTRATES
TRACER TECHNIQUES
ALKALINE EARTH METAL COMPOUNDS
ASCARIDAE
ASCHELMINTHES
CARBON ISOTOPES
CARBOXYLIC ACIDS
COENZYMES
EVEN-ODD NUCLEI
HELMINTHS
HYDROGEN ISOTOPES
HYDROXY ACIDS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
MEMBRANE PROTEINS
NEMATODES
NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
PARASITES
PROTEINS
REACTION KINETICS
STABLE ISOTOPES
TRANSITION ELEMENT COMPOUNDS
560300* - Chemicals Metabolism & Toxicology
550201 - Biochemistry- Tracer Techniques