Reference "Thiamin pyrophosphokinase is required for thiamin cofactor activation in Arabidopsis"

Reference ID

54973

Title

Thiamin pyrophosphokinase is required for thiamin cofactor activation in Arabidopsis

Source

Plant Mol Biol, 2007, vol. 65, pp. 151-162

Authors (4)

Ajjawi-I	Rodriguez-Milla-M-A
Cushman-J	Shintani-D-K

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.