Biochemistry, Department of


Date of this Version



The Journal of Biological Chemistry, Vol. 277, No. 36, Issue of September 6, pp. 33127–33131, 2002


Copyright 2002 by The American Society for Biochemistry and Molecular Biology, Inc.


The specificity of the ATP:corrinoid adenosyltransferase

(CobA) enzyme of Salmonella enterica serovar

Typhimurium LT2 for its nucleotide substrate was

tested using ATP analogs and alternative nucleotide donors.

The enzyme showed broad specificity for the nucleotide

base and required the 2-OH group of the ribosyl

moiety of ATP for activity. 31P NMR spectroscopy

was used to identify inorganic triphosphate (PPPi) as

the byproduct of the reaction catalyzed by the CobA

enzyme. Cleavage of triphosphate into pyrophosphate

and orthophosphate did not occur, indicating that

triphosphate cleavage was not required for release of

the adenosylcorrinoid product. Triphosphate was a

strong inhibitor of the reaction, with 85% of CobA activity

lost when the ATP/PPPi ratio present in the reaction

mixture was 1:2.5.