Faculty Collaboration Database

argE-encoded N-acetyl-L-ornithine deacetylase from Escherichia coli contains a dinuclear metalloactive site. J Am Chem Soc 2005 Oct 12;127(40):14100-7

Date

10/06/2005

Pubmed ID

16201833

DOI

10.1021/ja054081g

Scopus ID

2-s2.0-26444451028 (requires institutional sign-in at Scopus site)   25 Citations

Abstract

The catalytic and structural properties of the argE-encoded N-acetyl-L-ornithine deacetylase (ArgE) from Escherichia coli were investigated. On the basis of kinetic and ITC (isothermal titration calorimetry) data, Zn(II) binds to ArgE with Kd values that differ by approximately 20 times. Moreover, ArgE exhibits approximately 90% of its full catalytic activity upon addition of one metal ion. Therefore, ArgE behaves similarly to the aminopeptidase from Aeromonas proteolytica (AAP) in that one metal ion is the catalytic metal ion while the second likely plays a structural role. The N-acetyl-L-ornithine (NAO) deacetylase activity of ArgE showed a linear temperature dependence from 20 to 45 degrees C, indicating that the rate-limiting step does not change over this temperature range. The activation energy for NAO hydrolysis by ArgE was 25.6 kJ/mol when loaded with Zn(II) and 34.3 kJ/mol when loaded with Co(II). Electronic absorption and EPR (electron paramagnetic resonance) spectra of [Co x (ArgE)] and [CoCo(ArgE)] indicate that both divalent metal binding sites are five coordinate. In addition, EPR data show clear evidence of spin-spin coupling between the Co(II) ions in the active site but only after addition of a second equivalent of Co(II). Combination of these data provides the first physical evidence that the ArgE from E. coli contains a dinuclear Zn(II) active site, similar to AAP and the carboxypeptidase G2 from Pseudomonas sp. strain RS-16 (CPG2).

Author List

McGregor WC, Swierczek SI, Bennett B, Holz RC

Author

Brian Bennett D.Phil. Professor and Chair in the Physics department at Marquette University

MESH terms used to index this publication - Major topics in bold

Amidohydrolases
Binding Sites
Catalysis
Cobalt
Conductometry
Electron Spin Resonance Spectroscopy
Escherichia coli
Kinetics
Organometallic Compounds
Temperature
Time Factors
Zinc