Thermal equivalence criteria in the chemical deactivation and stabilization of acid phosphatase

Abstract

The complex mechanism of acid phosphatase thermal deactivation was analyzed and the dependence of the relevant thermodynamic and kinetic parameters from incubation temperature was determined. This enabled enzyme specific activity vs. time profiles to be predicted at any temperature. A variety of different chemicals were introduced in the enzyme incubation mixture that modified enzyme stability. In most cases, for each experimental run, an extremely close similarity was apparent of the corresponding experimental activity-time curve with that produced, at a different incubation temperature, by purely thermal deactivation. The latter temperature was lower (for chemical stabilizers) or higher (for inactivants) than that at which the actual deactivation took place. This result enabled the determination of an equivalent temperature for each environmental condition. Enzyme entrapment within a tight polymeric layer, produced by concentration polarization in an ultrafiltration membrane reactor, considerably increased enzyme stability. The corresponding deactivation profiles, however, were entirely different from purely thermal ones, thus indicating a different deactivation mechanism.