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Kinetic compensation and the role of cations in pectinesterase catalysis
- Sun, D., Wicker, L.
- Journal of agricultural and food chemistry 1999 v.47 no.4 pp. 1471-1475
- calcium chloride, energy, heat stability, pectins, calcium, citrus pulp, pectinesterase, activation energy, entropy, sodium, sodium chloride, temperature, enzyme activity, catalytic activity, grapefruits, inorganic ions
- The catalytic rate constant of thermostable pectinesterase (TS-PE) from Marsh grapefruit pulp was determined at pH 7 at temperatures between 25 and 60 degrees C. TS-PE activity was measured at NaCl concentrations of 0.05, 0.10, 0.15, and 0.20 M and at CaCl(2) concentrations of 0.005, 0.010, 0.015, and 0.020 M. For sodium- and calcium-added conditions, the kinetic functions of this reaction agreed with kinetic compensation relations. The isokinetic temperatures for sodium- and calcium-added conditions were 327.8 and 312.4 K, respectively. Different isokinetic temperatures and compensation parameters suggest that sodium and calcium uniquely affect TS-PE catalysis. This is the first demonstration of kinetic compensation in an enzyme-catalyzed reaction.