Thiamin pyrophosphokinase is required for thiamin cofactor activation in Arabidopsis |
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Authors: | Imad Ajjawi Miguel A Rodriguez Milla John Cushman David K Shintani |
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Institution: | (1) Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV 89557, USA;(2) Present address: Departamento de Biotecnología, Instituto Nacional de Investigación y Tecnología Agraría y Alimentaria, Madrid, 28040, Spain |
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Abstract: | Thiamin pyrophosphate (TPP) is an essential enzyme cofactor required for the viability of all organisms. Whether derived from
exogenous sources or through de novo synthesis, thiamin must be pyrophosphorylated for cofactor activation. The enzyme thiamin
pyrophosphokinase (TPK) catalyzes the conversion of free thiamin to TPP in plants and other eukaryotic organisms and is central
to thiamin cofactor activation. While TPK activity has been observed in a number of plant species, the corresponding gene/protein
has until now not been identified or characterized for its role in thiamin metabolism. Here we report the functional identification
of two Arabidopsis TPK genes, AtTPK1 and AtTPK2 and the enzymatic characterization of the corresponding proteins. AtTPK1 and AtTPK2 are biochemically redundant cytosolic
proteins that are similarly expressed throughout different plant tissues. The essential nature of TPKs in plant metabolism
is reflected in the observation that while single gene knockouts of either AtTPK1 or AtTPK2 were viable, the double mutant possessed a seedling lethal phenotype. HPLC analysis revealed the double mutant is nearly
devoid of TPP and instead accumulates the precursor of the TPK reaction, free thiamin. These results suggest that TPK activity
provides the sole mechanism by which exogenous and de novo derived thiamin is converted to the enzyme cofactor TPP. |
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Keywords: | Arabidopsis thaliana Cofactor activation Thiamin Thiamin pyrophosphate Thiamin pyrophosphokinase |
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