Characterization of Bacillus anthracis arginase: effects of pH, temperature, and cell viability on metal preference

Ryan J Viator¹ , Richard F Rest² , Ellen Hildebrandt³ and David J McGee³

¹Department of Biology, University of South Alabama, Mobile, AL 36688, USA

²Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA 19129, USA

³Department of Microbiology & Immunology, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA

author email corresponding author email

BMC Biochemistry 2008, 9:15doi:10.1186/1471-2091-9-15


Published:	3 June 2008

Abstract

Background

Arginase (RocF) hydrolyzes L-arginine to L-ornithine and urea. While previously characterized arginases have an alkaline pH optimum and require activation with manganese, arginase from Helicobacter pylori is optimally active with cobalt at pH 6. The arginase from Bacillus anthracis is not well characterized; therefore, this arginase was investigated by a variety of strategies and the enzyme was purified.

Results

The rocF gene from B. anthracis was cloned and expressed in E. coli and compared with E. coli expressing H. pylori rocF. In the native organisms B. anthracis arginase was up to 1,000 times more active than H. pylori arginase and displayed remarkable activity in the absence of exogenous metals, although manganese, cobalt, and nickel all improved activity. Optimal B. anthracis arginase activity occurred with nickel at an alkaline pH. Either B. anthracis arginase expressed in E. coli or purified B. anthracis RocF showed similar findings. The B. anthracis arginase expressed in E. coli shifted its metal preference from Ni > Co > Mn when assayed at pH 6 to Ni > Mn > Co at pH 9. Using a viable cell arginase assay, B. anthracis arginase increased dramatically when the cells were grown with manganese, even at final concentrations of <1 μM, whereas B. anthracis grown with cobalt or nickel (≥500 μM) showed no such increase, suggesting existence of a high affinity and specificity manganese transporter.

Conclusion

Unlike other eubacterial arginases, B. anthracis arginase displays unusual metal promiscuity. The unique properties of B. anthracis arginase may allow utilization of a specific metal, depending on the in vivo niches occupied by this organism.