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Published September 28, 2007 | Accepted Version + Published
Journal Article Open

Glutamine Phosphoribosylpyrophosphate Amidotransferase-independent Phosphoribosyl Amine Synthesis from Ribose 5-Phosphate and Glutamine or Asparagine

Abstract

Phosphoribosylamine (PRA) is the first intermediate in the common pathway to purines and thiamine and is generated in bacteria by glutamine phosphoribosylpyrophosphate (PRPP) amidotransferase (EC 2.4.2.14) from PRPP and glutamine. Genetic data have indicated that multiple, non-PRPP amidotransferase mechanisms exist to generate PRA sufficient for thiamine but not purine synthesis. Here we describe the purification and identification of an activity (present in both Escherichia coli and Salmonella enterica) that synthesizes PRA from ribose 5-phosphate and glutamine/asparagine. A purification resulting in greater than a 625-fold increase in specific activity identified 8 candidate proteins. Of the candidates, overexpression of AphA (EC 3.1.3.2), a periplasmic class B nonspecific acid phosphatase, significantly increased activity in partially purified extracts. Native purification of AphA to >95% homogeneity determined that the periplasmic L-asparaginase II, AnsB (EC 3.5.1.1), co-purified with AphA and was also necessary for PRA formation. The potential physiological relevance of AphA and AnsB in contributing to thiamine biosynthesis in vivo is discussed.

Additional Information

© 2007 the American Society for Biochemistry and Molecular Biology. Submitted on May 16, 2007. Revised on July 23, 2007. Accepted on August 8, 2007. Papers In Press, published online ahead of print August 8, 2007 This work was supported by competitive grant GM47296 from the NIH. Funds were also provided from a 21st Century Scientist Scholars Award from the J.S. McDonnell Foundation. I. Ramos was supported by a pre-doctoral fellowship from CONACyT (Mexico). We acknowledge Eugenio I. Vivas for his assistance in the cloning and purification of PurD and John Roth for his generosity in supplying the aphA15::Cm allele.

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Published - 28379.full.pdf

Accepted Version - KOEjbc07manu.pdf

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