A tomato enzyme catalyzing the phosphorylation of 3,4-dihydroxy-2-butanone

A riboflavin biosynthesis ribB mutant of Escherichia coli deficient of 3,4-dihydroxy-2-butanone 4-phosphate synthase was complemented with a cDNA library from Lycopersicon esculentum. The complementing gene was isolated and expressed in E. coli. The resulting protein was shown to specify a 62 kDa protein which phosphorylates dihydroxyacetone, both enantiomers of 3,4-dihydroxy-2-butanone, and several other aldoses and ketoses. Sequence analysis revealed homology to dihydroacetone kinases ( dak) genes from plants, animals, fungi and some eubacteria. Genes with similarity to the 5′ part of the dak gene from tomato were found in many other eubacteria. The physiological role of the dak gene is still incompletely known. A tomato enzyme with similarity to dihydroxyacetone kinases (DAK) from eukaryotes and several eubacteria catalyzes the phosphorylation of 3,4-dihydroxy-2-butanone to 3,4-dihydroxy-2-butanone 4-phosphate, an intermediate of riboflavin biosynthesis.