Progress of the Metabolic Pathway According to the Evolution of Organisms-Biosynthesis of Vitamin B Group and Coenzymes-

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1. Tne Biosynthetic Pathway of ThianinTwo ^<15>N-atoms of DL-[u, 3- ^<15>N]histidine were incorporated into the N-3 and amino-N atom at C-4 of the pyrimidine of thiamin. L-[2- ^<14>C]Histidine was incorporated directly into the pyrimidine. In contrast, the ^<15>N-atom of DL-[amino- ^<15N>]histidine and ^<14>C-atom of [U- ^<14>C]histidine, except C-2 of histidine, were not incorporated into the pyrimidine. We conclude that N-1, C-2, and N-3 of histidine are the origins of the N-3, C-4, and amino-N at C-4 of the pyrimidine in thiamin synthesized by Saccharomyces cerevisiae.The competitive investigation with ^<15>NH@_4Cl and various ^<14>N-compounds was carried out. The results revealed the origin of the N-1 atom of pyrimidine was derived from the N-1 atom of pyridoxine. The similarity of the stracture of the pyrimidine and pyridoxine suggests the N-1, C-2, and methyl carbon at C-2 of the pyrimidine was dirived from the N-1, C-2, and methyl carbon at C-2 of pyridoxine.In procaryotes, N, C … More -1, and C-2 of glycine are incorporated into N-1, C-4, and C-6 of the pyrimidine, respectively. We studied the incorporation of glycine into the pyrimidine in a eucaryote, Saccharomyces cerevisiae. The results rerealed that[1- ^<14>C]glycine was not incorporated into the pyrimidine, whereas[2- ^<14>C]glycine was incorporated into the pyrimidine at C-4 via histidine, a precursor of the C-4 of pyrimidine.2. The Biosvnthetic Pathway of the PyridoxineWe studied incorporation of L-[U- ^<14>C]alanine, [2- ^<14>C]pyruvate, [2- ^<14>C]acetate, [ ^<14>C]formate and[2- ^<14>C]glycerol into pyridoxine in Flavobacterium sp. No. 238-7. The respective radioactive carbon of alanine, pyruvate, acetate, formate and glycerol was incorporated into pyridoxine with high dilution. These findings suggest that the compounds tested are not the direct precursor.It has been reported that the C-5 and the hydroxymethyl carbon at C-5 of the pyridoxine is originated from the carbon atoms of glycolaldehyde. We revealed the active glycolaidehyde was dirived from the C-1 and C-2 atoms of fructose and incorporated into the C-5 and hydroxymethyl carbon at C-5 of the pyridoxine in Escherichia coli. Less