Publication: Activation and inhibition of pyruvate carboxylase from rhizobium etli
Issued Date
2011-11-15
Resource Type
ISSN
15204995
00062960
00062960
Other identifier(s)
2-s2.0-80755156281
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Mahidol University
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SCOPUS
Bibliographic Citation
Biochemistry. Vol.50, No.45 (2011), 9694-9707
Suggested Citation
Tonya N. Zeczycki, Ann L. Menefee, Sarawut Jitrapakdee, John C. Wallace, Paul V. Attwood, Martin St. Maurice, W. Wallace Cleland Activation and inhibition of pyruvate carboxylase from rhizobium etli. Biochemistry. Vol.50, No.45 (2011), 9694-9707. doi:10.1021/bi201276r Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/11433
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Title
Activation and inhibition of pyruvate carboxylase from rhizobium etli
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.