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

Journal Article · Tue May 05 00:00:00 EDT 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00383a027· OSTI ID:5856741

Grissom, C B; Willeford, O; Wedding, R T

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), Vol. 26:9
• Country of Publication: United States
• Language: English

Related Subjects

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