[Chemical modification of proteins by "smart" polymers]

The modification of proteinase inhibitor ovomucoid from duck eggs white by poly-N,N-diethylacrylamide having a low critical solution temperature (LCST) have been studied. Modification of free amino groups of lysine and N-terminal residue of ovomucoid is resulted in a significant decrease in the activity of the inhibitor toward trypsin and small decrease in the activity toward α-chymotrypsin. At heating of the solution of modified ovomucoid above the LCST transformation of the antitryptic centers of ovomucoid in antichymotryptic centers was observed. It was shown that this phenomenon is due to the hydrophobization the lysine residues localized in the reactive centers of the inhibitor while maintaining the structure of the "linkage loops". Therefore the α-chymotrypsine molecules began to interact with these residues, mistaking them for the residues of hydrophobic amino acids of antichymotryptic centers.