Novel /sup 18/O kinetic isotope effect in an. cap alpha. -chymotrypsin catalyzed transesterification

Journal Article · Wed Jan 30 00:00:00 EST 1980 · J. Am. Chem. Soc.; (United States)

OSTI ID:5439890

Wang, C L.A.; Trout, C M; Calvo, K C; Klapper, M H; Wong, L K

Reactions were started by injecting the nitrophenyl ester into a stoppered vial immersed in a constant-temperature bath (4/sup 0/C) containing a mixture of /sup 16/O plus /sup 18/O-ethanol, ..cap alpha..-chymotrypsin, and buffer. As the reaction proceeded, samples were withdrawn and injected into a gas chromatograph connected to a quadrupole mass spectrometer controlled by a data acquisition and processing system. The intensities from individual ions were displayed as a function of time to yield chromatographic peaks. Relative /sup 18/O enrichments were computed from the ratios of the peak areas, and the apparent KIE was then calculated from the ratio of enrichments in alcohol and ester. The values of the plateau KIE were less than or equal to 0.90 for all experiments. The apparent first-order rate constant can also be calculated from the magnitude of the initial burst and the slope of the zero-order absorbence increase. This apparent rate constant varies linearly with the ethanol concentration permitting calculation of the second-order rate associated with the formation of the ethyl ester product. 2 figures, 1 table.

• Research Organization: Ohio State Univ., Columbus
• OSTI ID: 5439890
• Journal Information: J. Am. Chem. Soc.; (United States), Vol. 102:3
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CHYMOTRYPSIN
ESTERIFICATION
ETHANOL
LABELLING
OXYGEN 18
ISOTOPE EFFECTS
ISOTOPE SEPARATION
CHEMICAL REACTION KINETICS
DATA ACQUISITION
GAS CHROMATOGRAPHY
MASS SPECTRA
PH VALUE
QUANTITY RATIO
TIME DEPENDENCE
ALCOHOLS
CHEMICAL REACTIONS
CHROMATOGRAPHY
ENZYMES
EVEN-EVEN NUCLEI
HYDROLASES
HYDROXY COMPOUNDS
ISOTOPES
KINETICS
LIGHT NUCLEI
NUCLEI
ORGANIC COMPOUNDS
OXYGEN ISOTOPES
PEPTIDE HYDROLASES
REACTION KINETICS
SEPARATION PROCESSES
SPECTRA
STABLE ISOTOPES
400302* - Organic Chemistry- Isotope Effects- (-1987)
400303 - Organic Chemistry- Isotope Exchange & Isotope Separation- (-1987)