Figure 3.

Thiamin biosynthesis pathway in plants. Thiamin is synthesized from pyrimidine and a thiazole moiety, both of which are synthesized in the chloroplast. The detailed description of the pathway is presented in the text. Abbreviations of the substrates: 5-aminoimidazole ribonucleotide (AIR), S-adenosylmethionine (SAM), nicotinamide adenine dinucleotide (NAD⁺), 4-amino-2-methyl-5-hydroxymethylpyrimidine phosphate (HMP-P), adenylated thiazole intermediate (ADT), 4-methyl-5-b-hydroxyethylthiazole phosphate (HET-P), thiamin monophosphate (TMP), thiamin pyrophosphate (TPP). Abbreviations of the enzymes: thiamin C synthase (THIC), -methyl-5-b-hydroxyethylthiazole phosphate (HET-P) synthase (THI1), thiamin monophosphate pyrophosphorylase (TH1), haloacid dehalogenase (HAD) family phosphatase (TH2), TPP kinases (TDPK).