Carbon kinetic isotope effects on pyruvate decarboxylation catalyzed by yeast pyruvate decarboxylase and models

Journal Article · Wed Apr 26 04:00:00 EST 1978 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00477a050· OSTI ID:6730611

Jordan, F; Kuo, D J; Monse, E U

Carbon-13 kinetic isotope effects were determined on pyruvate decarboxylation catalyzed by the enzyme yeast pyruvate decarboxylase and by thiamin, and in CHDT/sup +/Cl/sup -/ (2(1-carboxyl-1-hydroxyethyl)-3,4-dimethylthiazolium chloride). The CHDT/sup +/Cl/sup -/ gave an effect of 1.051 corresponding to the maximum isotope effect anticipated for CO/sub 2/ loss. Thiamin-catalyzed decarboxylation gave a pH-independent inverse isotope effect of 0.992 indicating that in that model decomposition of the covalent adduct formed between thiamin and pyruvate to reactants has a higher activation energy than the subsequent decarboxylation step. The enzymatic isotope effect was found to be normal varying from 1.002 at pH 7.5 to 1.011 at pH 5.0. At pH 5.00 the isotope effect was found to be temperature independent. The results were interpreted to mean that in the pH range employed decarboxylation is faster than the decomposition of the enzyme-bound thiamin-pyruvate covalent complex. A model is presented to account for the observed pH dependence of the enzymatic kinetic isotope effect.

• Research Organization: Rutgers-The State Univ., Newark, NJ
• OSTI ID: 6730611
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 100:9; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
AMINES
AZINES
AZOLES
CARBON 13
CARBON ISOTOPES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
DECARBOXYLASE
DECARBOXYLATION
ENZYMES
EVEN-ODD NUCLEI
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
ISOTOPE EFFECTS
ISOTOPES
KETO ACIDS
LIGHT NUCLEI
LYASES
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PYRIMIDINES
PYRUVIC ACID
STABLE ISOTOPES
TEMPERATURE DEPENDENCE
THIAMINE
THIAZOLES
VITAMIN B GROUP
VITAMINS