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Effectory Site in Escherichia coli Inorganic Pyrophosphatase is Revealed Upon Mutation at the Intertrimeric Interface
Author(s) -
Sitnik Tatyana,
Vain Julia,
Rodina Elena,
Nazarova Tatyana,
Kurilova Svetlana,
Vorobyeva Natalya,
Avaeva Svetlana
Publication year - 2003
Publication title -
iubmb life
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.132
H-Index - 113
eISSN - 1521-6551
pISSN - 1521-6543
DOI - 10.1080/1521654031000072139
Subject(s) - inorganic pyrophosphatase , escherichia coli , pyrophosphatase , chemistry , mutant , hydrolysis , kinetics , stereochemistry , biochemistry , residue (chemistry) , enzyme , pyrophosphate , gene , physics , quantum mechanics
Escherichia coli inorganic pyrophosphatase (E‐PPase) is a homohexamer formed from two trimers related by a two‐fold axis. The residue Asp26 participates in intertrimeric contacts. Kinetics of MgPPi hydrolysis by a mutant Asp26Ala E‐PPase is found to not obey Michaelis‐Menten equation but can be described within the scheme of activation of hydrolysis by a free PPi binding at an effectory subsite. Existence of such a subsite is confirmed by the finding that the free form of methylenediphosphonate activates MgPPi hydrolysis though its magnesium complex is a competitive inhibitor. The Asp26Ala variant is the first example of hexameric E‐PPase demonstrated to have an activatory subsite. IUBMB Life, 55: 37‐41, 2003