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ACS Chem Biol. 2013 Jan 18;8(1):242-8. doi: 10.1021/cb300364k. Epub 2012 Nov 2.

Anthranilate phosphoribosyl transferase (TrpD) generates phosphoribosylamine for thiamine synthesis from enamines and phosphoribosyl pyrophosphate.

Author information

1
Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.

Abstract

Anthranilate phosphoribosyl transferase (TrpD) has been well characterized for its role in the tryptophan biosynthetic pathway. Here, we characterized a new reaction catalyzed by TrpD that resulted in the formation of the purine/thiamine intermediate metabolite phosphoribosylamine (PRA). The data showed that 4- and 5-carbon enamines served as substrates for TrpD, and the reaction product was predicted to be a phosphoribosyl-enamine adduct. Isotopic labeling data indicated that the TrpD reaction product was hydrolyzed to PRA. Variants of TrpD that were proficient for tryptophan synthesis were unable to support PRA formation in vivo in Salmonella enterica. These protein variants had substitutions at residues that contributed to binding substrates anthranilate or phosphoribosyl pyrophosphate (PRPP). Taken together the data herein identified a new reaction catalyzed by a well-characterized biosynthetic enzyme, and both illustrated the robustness of the metabolic network and identified a role for an enamine that accumulates in the absence of reactive intermediate deaminase RidA.

PMID:
23101964
PMCID:
PMC3549051
DOI:
10.1021/cb300364k
[Indexed for MEDLINE]
Free PMC Article

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