Reactive Sites of the 21-kD Protein Inhibitor of Serine Proteinases from Potato Tubers

T. A. Valueva^*, T. A. Revina, and V. V. Mosolov

Bach Institute of Biochemistry, Russian Academy of Sciences, Leninskii pr. 33, Moscow, 117071 Russia; fax: (095) 954-2732; E-mail: inbio@glas.apc.org

^* To whom correspondence should be addressed.

Received February 5, 1999; Revision received May 20, 1999

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The effect of modifications of Met, Arg, and Lys residues on the inhibitory activity of a serine proteinase-inhibiting 21-kD protein from potato tubers has been studied. The data indicate that the 21-kD protein has two independent reactive sites for human leukocyte elastase (or chymotrypsin) and trypsin. It is concluded that the 21-kD inhibitor has Met and Arg residues in the P1 position of the reactive sites responsible for interactions with elastase (or chymotrypsin) and trypsin. It is shown that the 21-kD protein is capable of forming a triple complex binding simultaneously one molecule of trypsin and one molecule of chymotrypsin.

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KEY WORDS: chemical modification, serine proteinase inhibitor, human leukocyte elastase, chymotrypsin, trypsin, potato tubers

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