Simple jQuery Dropdowns
Please use this identifier to cite or link to this item:
Title: Activation and inhibition of pyruvate carboxylase from rhizobium etli
Authors: Tonya N. Zeczycki
Ann L. Menefee
Sarawut Jitrapakdee
John C. Wallace
Paul V. Attwood
Martin St. Maurice
W. Wallace Cleland
University of Wisconsin Madison, Institute for Enzyme Research
Marquette University
Mahidol University
University of Adelaide
University of Western Australia
Keywords: Biochemistry, Genetics and Molecular Biology
Issue Date: 15-Nov-2011
Citation: Biochemistry. Vol.50, No.45 (2011), 9694-9707
Abstract: While crystallographic structures of the R. etli pyruvate carboxylase (PC) holoenzyme revealed the location and probable positioning of the essential activator, Mg 2+ , and nonessential activator, acetyl-CoA, an understanding of how they affect catalysis remains unclear. The current steady-state kinetic investigation indicates that both acetyl-CoA and Mg 2+ assist in coupling the MgATP-dependent carboxylation of biotin in the biotin carboxylase (BC) domain with pyruvate carboxylation in the carboxyl transferase (CT) domain. Initial velocity plots of free Mg 2+ vs pyruvate were nonlinear at low concentrations of Mg 2+ and a nearly complete loss of coupling between the BC and CT domain reactions was observed in the absence of acetyl-CoA. Increasing concentrations of free Mg 2+ also resulted in a decrease in the K a for acetyl-CoA. Acetyl phosphate was determined to be a suitable phosphoryl donor for the catalytic phosphorylation of MgADP, while phosphonoacetate inhibited both the phosphorylation of MgADP by carbamoyl phosphate (K i = 0.026 mM) and pyruvate carboxylation (K i = 2.5 mM). In conjunction with crystal structures of T882A R. etli PC mutant cocrystallized with phosphonoacetate and MgADP, computational docking studies suggest that phosphonoacetate could coordinate to one of two Mg 2+ metal centers in the BC domain active site. Based on the pH profiles, inhibition studies, and initial velocity patterns, possible mechanisms for the activation, regulation, and coordination of catalysis between the two spatially distinct active sites in pyruvate carboxylase from R. etli by acetyl-CoA and Mg 2+ are described. © 2011 American Chemical Society.
ISSN: 15204995
Appears in Collections:Scopus 2011-2015

Files in This Item:
There are no files associated with this item.

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.