Transferases;
Transferring alkyl or aryl groups, other than methyl groups;
Transferring alkyl or aryl groups, other than methyl groups (only sub-subclass identified to date)
BRITE hierarchy

4-amino-2-methyl-5-(diphosphooxymethyl)pyrimidine:2-[(2R,5Z)-2-carboxy-4-methylthiazol-5(2H)-ylidene]ethyl phosphate 4-amino-2-methylpyrimidine-5-methenyltransferase (decarboxylating)

(1) 4-amino-2-methyl-5-(diphosphooxymethyl)pyrimidine + 2-[(2R,5Z)-2-carboxy-4-methylthiazol-5(2H)-ylidene]ethyl phosphate = diphosphate + thiamine phosphate + CO2 [RN:R11312];
(2) 4-amino-2-methyl-5-(diphosphooxymethyl)pyrimidine + 2-(2-carboxy-4-methylthiazol-5-yl)ethyl phosphate = diphosphate + thiamine phosphate + CO2 [RN:R10712];
(3) 4-amino-2-methyl-5-(diphosphooxymethyl)pyrimidine + 4-methyl-5-(2-phosphooxyethyl)thiazole = diphosphate + thiamine phosphate [RN:R03223]

R03223 R10712 R11312
Reaction

4-amino-2-methyl-5-(diphosphooxymethyl)pyrimidine [CPD:C04752];
2-[(2R,5Z)-2-carboxy-4-methylthiazol-5(2H)-ylidene]ethyl phosphate [CPD:C20246];
2-(2-carboxy-4-methylthiazol-5-yl)ethyl phosphate [CPD:C20247];
4-methyl-5-(2-phosphooxyethyl)thiazole [CPD:C04327]

The enzyme catalyses the penultimate reaction in thiamine de novo biosynthesis, condensing the pyrimidine and thiazole components. The enzyme is thought to accept the product of EC 2.8.1.10, thiazole synthase, as its substrate. However, it has been shown that in some bacteria, such as Bacillus subtilis, an additional enzyme, thiazole tautomerase (EC 5.3.99.10) converts that compound into its tautomer 2-(2-carboxy-4-methylthiazol-5-yl)ethyl phosphate, and that it is the latter that serves as the substrate for the synthase. In addition to this activity, the enzyme participates in a salvage pathway, acting on 4-methyl-5-(2-phosphooxyethyl)thiazole, which is produced from thiamine degradation products. In yeast this activity is found in a bifunctional enzyme (THI6) and in the plant Arabidopsis thaliana the activity is part of a trifunctional enzyme (TH1).

EC 2.5.1.3 created 1965, modified 2015