Thiamin pyrophosphorylase

Vitamin Bi is an essential co-factor for several enzymes of carbohydrate metabolism such as transketolase, pyruvate dehydrogenase (PDH), pyruvate decarboxylase and a-ketoglutarate dehydrogenase. To become the active co-factor thiamin pyrophosphate (TPP), thiamin has to be salvaged by thiamin pyrophosphokinase or synthesized de novo. In Escherichia coli and Saccharomyces cerevisiae thiamin biosynthesis proceeds via two branches that have to be combined. In the pyrimidine branch, 4-amino-5-hydroxymethy-2-methylpyrimidine (PIMP) is phosphorylated to 4-amino-2-methyl-5-hydroxymethyl pyrimidine diphosphate (PIMP-PP) by the enzyme HMP/HMP-P kinase (ThiD) however, the step can also be catalyzed by pyridoxine kinase (PdxK), an enzyme also responsible for the activation of vitamin B6 (see below). The second precursor of thiamin biosynthesis, 5-(2-hydroxyethyl)-4-methylthiazole (THZ), is activated by THZ kinase (ThiM) to 4-methyl-5-(2-phosphoethyl)-thiazole (THZ-P), and then the thia-zole and pyrimidine moieties, HMP-PP and THZ-P, are combined to form thiamin phosphate (ThiP) by thiamin phosphate synthase (ThiE). The final step, pyrophosphorylation, yields TPP and is carried out by thiamin pyrophosphorylase (TPK). 

EC 2.5.1.3 Thiamin-phosphate pyrophosphorylase 2-Methyl-4-amino-5-hydroxymethylpyrimide diphosphate + 4-methyl-5-(2-phosphono-oxyethyl)-thiazole pyrophosphate + thiamine monophosphate FGM... 

S Additional information <2, 4> (<4> enzyme is probably different from previously isolated HMP kinase, because the subunit molecular masses are significantly different [4] <4> bifunctional hydroxymethylpyrimidine kinase/phosphomethylpyrimidine kinase [5] <2> bifunctional hydroxy-pyrimidine kinase/thiamin-phosphate pyrophosphorylase [3]) [3-5]... 

Kim, Y.S. Nosaka, K. Downs, D.M. Kwak, J.M. Park, D. Chung, I.K. Nam, H.G. A Brassica cDNA clone encoding a bifunctional hydroxymethylpyrimidine kinase/thiamin-phosphate pyrophosphorylase involved in thiamin biosynthesis. Plant Mol. Biol., 37, 955-966 (1998)... 

Saccharomyces cerevisiae (mutant resistant to 2-amino-4-methyl-5- -hy-droxyethylthiazole, an antimetabolite of 4-methyl-5-/l-hydroxyethylthia-zole, deficient in activity of both EC 2.5.1.3 and EC 2.7.1.50 [2] bifunctional enzyme with hydroxyethylthiazole kinase and thiamine-phosphate pyrophosphorylase activity [2]) [1, 2]... 

S ATP + 4-methyl-5-(2-hydroxyethyl)thiazole <1, 2> (<1> enzyme involved in biosynthesis of thiamine [1] <1> the bifunctioinal enzyme hydroxyethylthiazole kinase/thiamine-phosphate pyrophosphorylase catalyzes two sequential steps in the synthesis of thiamin monophosphate from hydroxyethylthiazole [2] <2> the enzyme is a salvage enzyme in the thiamin biosynthetic pathway and enables the cell to use recycled 4-methyl-5-j8-hydroxyethylthiazole as an alternative to its synthesis from 1-deoxy-o-xylulose-5-phosphate, cysteine, and tyrosine [3]) (Reversibility <1, 2> [1,2,3]) [1,2, 3]... 

Kawasaki, Y. Copurification of hydroxyethylthiazole kinase and thiamine-phosphate pyrophosphorylase of Saccharomyces cerevisiae characterization of hydroxyethylthiazole kinase as a bifunctional enzyme in the thiamine biosynthetic pathway. J. Bacteriol., 175, 5153-5158 (1993)... 

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