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Isotope effect studies of the chemical mechanism of nicotinamide adenine dinucleotide malic enzyme from Crassula

Journal Article · · Biochemistry; (United States)
DOI:https://doi.org/10.1021/bi00383a027· OSTI ID:5856741
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The /sup 13/C primary kinetic isotope effect on the decarboxylation of malate by nicotinamide adenine dinucleotide malic enzyme from Crassula argentea is 1.0199 +/- 0.0006 with proteo L-malate-2-H and 1.0162 +/- 0.0003 with malate-2-d. The primary deuterium isotope effect is 1.45 +/- 0.10 on V/K and 1.93 +/- 0.13 on V/sub max/. This indicates a stepwise conversion of malate to pyruvate and CO/sub 2/ with hydride transfer preceding decarboxylation, thereby suggesting a discrete oxaloacetate intermediate. This is in agreement with the stepwise nature of the chemical mechanism of other malic enzymes despite the Crassula enzyme's inability to reduce or decarboxylate oxaloacetate. Differences in morphology and allosteric regulation between enzymes suggest specialization of the Crassula malic enzyme for the physiology of crassulacean and acid metabolism while maintaining the catalytic events founds in malic enzymes from animal sources.
Research Organization:
Univ. of California, Riverside
OSTI ID:
5856741
Journal Information:
Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:9; ISSN BICHA
Country of Publication:
United States
Language:
English

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Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BIOCHEMICAL REACTION KINETICS
CARBON 13
CARBON ISOTOPES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
COENZYMES
DECARBOXYLATION
DEUTERIUM COMPOUNDS
ENZYMES
EVEN-ODD NUCLEI
HEMIACETAL DEHYDROGENASES
HYDROGEN COMPOUNDS
HYDROXY ACIDS
ISOTOPE EFFECTS
ISOTOPES
KETO ACIDS
KINETICS
LIGHT NUCLEI
MALIC ACID
NAD
NUCLEI
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PLANTS
PYRUVIC ACID
REACTION KINETICS
STABLE ISOTOPES