Kinetic Aspects of the Irreversible Thermal Inactivation of Enzymes

Abstract

Zero-dimensional power balance calculations are performed for a quasi-static, purely Ohmically heated field-reversed configuration. Without compression, the constraint imposed by radial pressure balance limits the power input. Estimates of the energy loss from impurity line radiation as well as from classical and anomalous transport are given. Effects of cold puff gas injection are also investigated.

Catalytic activity and thermostability of dehydrogenase conjugates with cortisol and progesterone

“…As it was shown by us earlier (18)(19)(20)(21)(22) the rate constants feo calculated with eq 1 were close to the rate constants of the dimeric dehydrogenases dissociation, fei (see eq 2); i.e. the biocatalyst dissociation may be the limiting stage of the enzyme thermoinactivation.…”

“…The experimental data obtained by us (18)(19)(20)(21)(22) support the assumption that the dissociative inactivation of dimeric (or tetrameric) dehydrogenases may be described by the following simplest scheme:…”

“…Figure 6 shows the semilogarithmic anamorphoses of kinetic curves of the catalytic activity loss at 40 °C for the initial MDH (a), the control enzyme incubated in the water-DMFA (10%) mixture (b), and conjugate MDH-3-PROG-16 (c). As seen, the biocatalyst inactivation at its various initial concentrations ranged from 0.005 to 0.1 mg/mL and is described by the first-order equation below, which gives a fair approximation for inactivation of two other dehydrogenases (G6PDH, LDH) and their numerous conjugates at various concentrations and different temperatures (18)(19)(20)(21)(22). In all the cases, the rate constants of the biocatalyst inactivation, fej", were strongly dependent on the initial protein concentration.…”

“…enzyme concentration, [E]o (18)(19)(20)(21)(22), where feo is the rate constant of the protein inactivation at its infinite dilution, A is the reverse rate in M"1 s and dependent on temperature, and [E]o is the initial concentration of subunit enzyme or its conjugate.…”

“…Analysis of the temperature dependences of the effective rate constants for the dehydrogenase inactivation, fe¡n, could not be overestimated, since the temperature course 0 Protein concentration equaled 5 X 10"3 mg/mL. of these constants, as a rule, is < complicated owing to the effect of the initial protein concentration on their values (18)(19)(20)(21)(22)36). Only an analysis of the temperature dependences of ko constants, obtained by an extrapolation of A¡" to "zero" concentration of a biocatalyst (see Figure 7), can have a definite physical meaning.…”