In enzymology, a hydroxyethylthiazole kinase (EC 2.7.1.50) is an enzyme that catalyzes the chemical reaction

ATP + 4-methyl-5-(2-hydroxyethyl)thiazole ${\displaystyle \rightleftharpoons }$ ADP + 4-methyl-5-(2-phosphonooxyethyl)thiazole

Thus, the two substrates of this enzyme are ATP and 4-methyl-5-(2-hydroxyethyl)thiazole, whereas its two products are ADP and 4-methyl-5-(2-phosphonooxyethyl)thiazole.

This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing groups (phosphotransferases) with an alcohol group as acceptor. The systematic name of this enzyme class is ATP:4-methyl-5-(2-hydroxyethyl)thiazole 2-phosphotransferase. Other names in common use include hydroxyethylthiazole kinase (phosphorylating), and 4-methyl-5-(beta-hydroxyethyl)thiazole kinase. This enzyme participates in thiamine metabolism. Thiamine pyrophosphate (TPP), a required cofactor for many enzymes in the cell, is synthesised de novo in Salmonella typhimurium.^[1]

In Saccharomyces cerevisiae, hydroxyethylthiazole kinase expression is regulated at the mRNA level by intracellular thiamin pyrophosphate.^[2]

As of late 2007, 6 structures have been solved for this class of enzymes, with PDB accession codes 1C3Q, 1EKK, 1EKQ, 1ESJ, 1ESQ, and 1V8A.