Interaction between Duodenase and alpha₁-Proteinase Inhibitor

I. P. Gladysheva^1*, N. A. Popykina¹, T. S. Zamolodchikova², and N. I. Larionova¹

¹Department of Chemical Enzymology, School of Chemistry, Lomonosov Moscow State University, Moscow, 119899 Russia; fax: (095) 939-5417; E-mail: gladysheva@enzyme.chem.msu.ru

²Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya 16/10, Moscow, 117871 Russia; fax: (095) 310-7007

^* To whom correspondence should be addressed.

Received November 1, 2000; Revision received February 14, 2001

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The interaction between duodenase, a newly recognized serine proteinase belonging to the small group of Janus-faced proteinases, and alpha₁-proteinase inhibitor (alpha₁-PI) from human serum was investigated. The stoichiometry of the inhibition was 1.2 mol/mol. The presence of a stable enzyme-inhibitor complex was shown by SDS-PAGE. The mechanism of interaction between duodenase and alpha₁-PI was shown to be of the suicide type. The equilibrium and inhibition constants are 13 ± 3 nM and (1.9 ± 0.3)·10⁵ M^-1·sec^-1, respectively. Based on the association rate constant of the enzyme-inhibitor complex and localization of duodenase and alpha₁-PI in identical compartments, alpha₁-PI is suggested to be a duodenase inhibitor in vivo.

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KEY WORDS: duodenase, alpha₁-proteinase inhibitor

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