[Role of hydrophobic interactions in manifestation of catalytic activity of lipolytic enzymes]. / Rol' gidrofobnykh vzaimodeistvii v proiavlenii kataliticheskoi aktivnosti lipoliticheskikh fermentov.

Kinetics is studied of enzymatic hydrolysis of different substrates of soluble and immobilized cotton lipase. At least two stages of enzymatic lipolysis are found to take place, which precede the formation of Mikhaelis complex: 1) the enzyme adsorption on substrate phase surface and 2) lipase activation. The latter is accompanied by the formation of local chamber on phase contact area in which the hydrolysis occurs. It is suggested on the basis of data on the inhibition by a number of phenylcarbonic acids and fluoride ions, on the hydrolysis rate of soluble and insoluble substrates, catalysed by different immobilized lipases, that there are three regions in the active center of lipolytic enzymes: 1) a region responsible for the "recognition" of substrate phase surface; 2) a binding region, participating in hydrophobic interaction with a single substrate molecule, located in the insoluble phase; 3) catalytical region. A hypothetic scheme of lipid enzymatic hydrolysis at phase contact area is given.

[The relationship of cottonseed's triacetinase]. / Vzanmosvitaz" triatsetinaz semian khlopchatnika

A multiplicity of triacetinase forms in cotton seeds was studied. Three triacetinases (A, B and C) were shown to undergo reciprocal conversions under storage and during some purification procedures (effect of pH, ionic strength, ion-exchange chromatography, concentration, lyophilization, etc.). On the other hand, the presence of different triacetinase forms in cotton seeds cannot be considered an artefact of isolation, since the formation of more active low-molecular forms from inactive high-molecular forms occurs during seed germination. A correlation between the activity and stability of the enzymes on one hand and their quaternary structure on the other, is discussed.