InterPro domain: IPR005477

1-Deoxy-D-xylulose-5-phosphate synthase (DXP synthase) is a regulatory enzyme of the mevalonate-independent pathway involved in terpenoid biosynthesis. Terpeniods are plant natural products with important pharmaceutical activity. DXP synthase is a thiamine diphosphate-dependent enzyme related to transketolase and the pyruvate dehydrogenase E1-beta subunit. DXP synthase is found in bacteria (gene dxs)and plants (gene CLA1) which catalyzes the thiamine pyrophosphoate-dependent acyloin condensation reaction between carbon atoms 2 and 3 of pyruvate and glyceraldehyde 3-phosphate to yield 1-deoxy-D-xylulose-5-phosphate (dxp), a precursor in the biosynthetic pathway to isoprenoids, thiamine (vitamin B1), and pyridoxol (vitamin B6). DXP synthase is evolutionary related to TK. The N-terminal section contains a histidine residue which appears to function in proton transfer during catalysis [ 1 ]. In the central section there are conserved acidic residues that are part of the active cleft and may participate in substrate-binding [ 2 ]. This family includes transketolase enzymes 2.2.1.1 , and also partially matches to 2-oxoisovalerate dehydrogenase beta subunit P37941 1.2.4.4 . Both these enzymes utilise thiamine pyrophosphate as a cofactor, suggesting there may be common aspects in their mechanism of catalysis.

1. Three-dimensional structure of transketolase, a thiamine diphosphate dependent enzyme, at 2.5 A resolution. EMBO J. 11, 2373-9