[Effect of medium viscosity on the activity of myosin ATPase]. / Vliianie viazkosti sredy na aktivnost' miozinovoi ATFazy.

The influence of increased medium viscosity on the activity of myosin Ca2+-ATPase has been studied in 28, 45 and 60% water-sucrose solutions at 25 degrees C. In the wide range of viscosities (10 divided by 430 mp) the rate constant of ATP hydrolysis displays the negative power-law dependence on solution viscosity with an index approximately -0,5. The obtained data confirm an idea about the existence of direct connection between the low-frequency liquid relaxations and structural dynamics of proteins and enzymes.

[Activation energy of enzymatic hydrolysis of different substrates of alpha-chymotrypsin]. / Energiia aktivatsii fermentativnogo gidroliza razlichnykh substratov alpha-khimotripsina.

Analysis of the experimental data for the series of alpha-chymotrypsin-catalyzed reactions of ester hydrolysis was carried out on the basis of modern elementary act theory of chemical processes. It was concluded that activation energy of considered reactions is attributed by repulsion potential for nucleophilic particle and carbonyl centre. It was supposed that the reason for abrupt changes of activation energy accompanying small enzyme-substrate complex structure shifts lies in the corresponding changes of carbonyl centre polarizability governed by its electrophilic environment.