argE-Encoded N-Acetyl-l-Ornithine Deacetylase from Escherichia coli Contains a Dinuclear Metalloactive Site

Authors

Wade C. McGregor, Utah State UniversityFollow
Sabina I. Swierczek, Utah State UniversityFollow
Brian Bennett, Marquette UniversityFollow
Richard C. Holz, Marquette UniversityFollow

Document Type

Article

Language

eng

Format of Original

8 p.

Publication Date

10-2005

Publisher

American Chemical Society

Source Publication

Journal of the American Chemical Society

Source ISSN

0002-7863

Original Item ID

doi: 10.1021/ja054081g

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 K_d values that differ by ∼20 times. Moreover, ArgE exhibits ∼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 °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·(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).

Comments

Accepted version. Journal of the American Chemical Society, Vol. 127, No. 40 (October 2005): 14100-14107. DOI. © 2005 American Chemical Society. Used with permission.

Brian Bennett was affiliated with Medical College of Wisconsin at the time of publication.

Richard Holz was affiliated with Utah State University at the time of publication.

Recommended Citation

McGregor, Wade C.; Swierczek, Sabina I.; Bennett, Brian; and Holz, Richard C., "argE-Encoded N-Acetyl-l-Ornithine Deacetylase from Escherichia coli Contains a Dinuclear Metalloactive Site" (2005). Physics Faculty Research and Publications. 27.
https://epublications.marquette.edu/physics_fac/27