抄録
Biosynthetic pathway of the pyrimidine moiety of thiamin was studied. Procaryotes and eucaryotes have different biosynthetic pathways for the pyrimidine. In procaryotes, the pyrimidine is formed by ring expansion of imidazole accompanied insertion of C-4', C-5' fragment of ribose of 5-aminoimidazole ribonucleotide, a intermediate of purine biosynthesis. In eucaryotes, N-3, C-4, and amino-N attached at C-4 of the pyrimidine are derived from N-1, C-2 and N-3 of the imidazole ring of histidine and the three carbon unit of C-6, C-5 and C-7 is originated from C-1, C-2 and C-3 of ribose.
