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Journal of Bacteriology, March 2007, p. 2210-2218, Vol. 189, No. 6
0021-9193/07/$08.00+0     doi:10.1128/JB.01665-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Reassessment of the Late Steps of Coenzyme B12 Synthesis in Salmonella enterica: Evidence that Dephosphorylation of Adenosylcobalamin-5'-Phosphate by the CobC Phosphatase Is the Last Step of the Pathway{triangledown}

Carmen L. Zayas and Jorge C. Escalante-Semerena*

Department of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin

Received 27 October 2006/ Accepted 22 December 2006

We report that cobC strains of Salmonella enterica serovar Typhimurium are impaired in the ability to salvage cobyric acid (Cby), a de novo corrin ring biosynthetic intermediate, under aerobic growth conditions. In vivo and in vitro evidence support the conclusion that this new phenotype of cobC strains is due to the inability of serovar Typhimurium to dephosphorylate adenosylcobalamin-5'-phosphate (AdoCbl-5'-P), the product of the condensation of {alpha}-ribazole-5'-phosphate ({alpha}-RP) and adenosylcobinamide-GDP by the AdoCbl-5'-P synthase (CobS, EC 2.7.8.26) enzyme. Increased flux through the 5,6-dimethylbenzimidazole and cobinamide (Cbi) activation branches of the nucleotide loop assembly pathway in cobC strains restored AdoCbl-5'-P synthesis from Cby in a cobC strain. The rate of the CobS-catalyzed reaction was at least 2 orders of magnitude higher with {alpha}-RP than with {alpha}-ribazole as substrate. On the basis of the data reported herein, we conclude that removal of the phosphoryl group from AdoCbl-5'-P is the last step in AdoCbl biosynthesis in serovar Typhimurium and that the reaction is catalyzed by the AdoCbl-5'-P phosphatase (CobC) enzyme. Explanations for the correction of the Cby salvaging phenotype are discussed.

* Corresponding author. Mailing address: Department of Bacteriology, University of Wisconsin, 144A Enzyme Institute, 1710 University Avenue, Madison, WI 53726-4087. Phone: (608) 262-7379. Fax: (608) 265-7909. E-mail: escalante{at}bact.wisc.edu.

{triangledown} Published ahead of print on 5 January 2007.

Journal of Bacteriology, March 2007, p. 2210-2218, Vol. 189, No. 6
0021-9193/07/$08.00+0     doi:10.1128/JB.01665-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Fan, C., Bobik, T. A. (2008). The PduX Enzyme of Salmonella enterica Is an L-Threonine Kinase Used for Coenzyme B12 Synthesis. J. Biol. Chem. 283: 11322-11329 [Abstract] [Full Text]  
  • Zayas, C. L., Claas, K., Escalante-Semerena, J. C. (2007). The CbiB Protein of Salmonella enterica Is an Integral Membrane Protein Involved in the Last Step of the De Novo Corrin Ring Biosynthetic Pathway. J. Bacteriol. 189: 7697-7708 [Abstract] [Full Text]  
  • Escalante-Semerena, J. C. (2007). Conversion of Cobinamide into Adenosylcobamide in Bacteria and Archaea. J. Bacteriol. 189: 4555-4560 [Full Text]  


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