Lactate dehydrogenase-catalyzed stereospecific hydrogen atom transfer from reduced nicotinamide adenine dinucleotide to dicarboxylate radicals
The dicarboxylate radical was generated in an N/sub 2/O-saturated fumarate solution by high energy ionizing radiation. When NADH was present in the solution, product analysis indicated a stoichiometry of 2 molecules of the radical reacted with 1 NADH molecule to form 2 malate and 1 enzymatically active NAD/sup +/ molecules. In a similar experiment using tritium label on position A of NADH, due to an isotope effect, only 10 percent of the label was transferred to malate; most of the remaining tritium was found in the NAD/sup +/ formed. When lactate dehydrogenase was added, however, no label was detectable in NAD/sup +/, and over 80 percent of the tritium lost from NADH was found in malate. The stereospecific transfer of the hydrogen atom from lactate dehydrogenase-bound NADH to the dicarboxylate radical suggested that the free radical reaction must have taken place at the active site. The hydrogen atom transfer was inhibited by oxamate. Results from flow experiments in which an irradiated fumarate solution was mixed with a solution of lactate dehydrogenase and NADH are in support of a mechanism in which the hydrogen atom transfer occurs in the first oxidation step. (auth)
- Research Organization:
- State Univ. of New York Downstate Medical Center, Brooklyn
- OSTI ID:
- 7292997
- Journal Information:
- J. Biol. Chem.; (United States), Vol. 250:18
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
HYDROGEN
TRANSFER REACTIONS
BIOCHEMICAL REACTION KINETICS
DICARBOXYLIC ACIDS
LACTATE DEHYDROGENASE
NAD
OXIDATION
RADICALS
STEREOCHEMISTRY
TRITIUM
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
COENZYMES
CRYOGENIC FLUIDS
DEHYDROGENASES
DIRECT REACTIONS
ELEMENTS
ENZYMES
FLUIDS
HYDROGEN ISOTOPES
ISOTOPES
KINETICS
LIGHT NUCLEI
NONMETALS
NUCLEAR REACTIONS
NUCLEI
NUCLEOTIDES
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
RADIOISOTOPES
REACTION KINETICS
YEARS LIVING RADIOISOTOPES
550200* - Biochemistry