Active Dimeric Form of Inorganic Pyrophosphatase from Escherichia coli

Yu. P. Vainonen¹, N. N. Vorobyeva¹, S. A. Kurilova², T. I. Nazarova², E. V. Rodina^1*, and S. M. Avaeva²

¹Faculty of Chemistry and ²Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119992, Russia; fax: (7-095) 939-3181; E-mail: rodina@belozersky.msu.ru

^* To whom correspondence should be addressed.

Received February 14, 2003; Revision received March 13, 2003

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A dimeric form can be obtained from native hexameric Escherichia coli inorganic pyrophosphatase (E-PPase) by destroying the hydrophobic intersubunit contacts, and it has been shown earlier to consist of the subunits of different trimers. The present paper is devoted to the kinetic characterization of such a “double-decked” dimer obtained by the dissociation of either the native enzyme or the mutant variant Glu145Gln. The dimeric form of the native inorganic pyrophosphatase was shown to retain high catalytic efficiency that is in sharp contrast to the dimers obtained as a result of the mutations at the intertrimeric interface. The dimeric enzymes described in the present paper, however, have lost the regulatory properties, in contrast to the hexameric and trimeric forms of the enzyme.

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KEY WORDS: inorganic pyrophosphatase, dimer, activity, regulation

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