The application of thermodynamics to biochemical systems has given rise to the new discipline of biochemical thermodynamics [1–4], an important part of which is the thermodynamics of enzymatic reactions. The interest in this area extends beyond biochemistry, since enzymes appear to be promising catalysts for use in industrial organic sythesis [5–7]. The accumulated data in the literature on enzymatic reactions (equilibrium, enthalpy, entropy, Gibbs energy, heat capacity) need to be systematized and scrutinized. Armstrong et al. [8–12] have made an important contribution towards this goal by classifying the various sources of information.

Thermodynamics of Enzymatic Reactions

Thermochemistry of the l-asparagine hydrolysis reaction catalyzed by l-asparaginase

Simple industrial method for determination of activity of asparaginase and some other enzymes.

The active site of chymotrypsin molecule (approximated by a sphere with radius of 20 A) was taken as the largest cavity on the enzyme surface The volume inside the approximating sphere is sufficient for placement of 95% of non-hydrogen atoms of the enzyme The active site cavity is localized in a spherical sector with solid angle of 80° whose axis passes through the CB-atom of the Ser195 residue The volume of the active site cavity is about 2700 A3 (8% of the volume of the approximating sphere) as computed by the Monte-Carlo method from known X-ray data The size and shape of the active site cavity is sufficient for entrance of significantly large fragments (more than 60 non-hydrogen atoms) of the substrate molecule At the active site cavity bottom, there is a narrow compartment adjacent to an oxy-anion hollow and accessible to water but not to substrate molecules The water molecules inside this narrow compartment can take part in heat exchange with the external medium during different steps of the enzymatic process

V.K. Antonov

Papers

Thermochemistry of the N-acetylphenylalanine methylester hydrolysis reaction catalyzed by α-chymotrypsin