title: Binding of substrate at the effector site of pyrophosphatase increases the rate of its hydrolysis at the active site.
abstract: It is shown that in addition to the active site, each subunit of Escherichia coli inorganic pyrophosphatase (E-PPase) contains an extra binding site for the substrate magnesium pyrophosphate or its non-hydrolyzable analog magnesium methylenediphosphonate. The occupancy of the extra site stimulates the substrate conversion. Binding affinity of this site decreased or disappeared upon the conversion of E-PPase into a trimeric form or introduction of point mutations. However, when the slowly hydrolyzed substrate, lanthanum pyrophosphate (LaPP(i)), is used, the extra site was revealed in all enzyme forms of E-PPase and of Y-PPase (Saccharomyces cerevisiae PPase), resulting in about 100-fold activation of hydrolysis. A hypothesis on the localization of the extra site and the mechanism of its effect in E-PPase is presented.
authors.affiliation: Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119992, Russia.
authors.forename: T S
authors.initials: TS
authors.lastname: Sitnik
authors.forename: S M
authors.initials: SM
authors.lastname: Avaeva
mesh_terms: D001665:Binding Sites; D011756:Diphosphates / Q000737:chemistry*; D004926:Escherichia coli / Q000201:enzymology*; D006868:Hydrolysis; D043564:Inorganic Pyrophosphatase / Q000737:chemistry* / Q000235:genetics; D007811:Lanthanum / Q000737:chemistry; D017616:Magnesium Compounds / Q000737:chemistry*; D015394:Molecular Structure; D009154:Mutation; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D011756:Diphosphates; D017616:Magnesium Compounds; D007811:Lanthanum; C034732:magnesium pyrophosphate; D043564:Inorganic Pyrophosphatase