Biosynthesis of Corrinoids and Porphyrinoids. IX. Studies on the Origin of Oxygen of Uroporphyrinogen III in Arthrobacter hyalinus

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The biosynthetic origin of carbonyl oxygen of uroporphyrinogen III was investigated. A model experiment using methyl benzoate labeled with ^<13>C and ^<18>O revealed isotope shifts of 0.015 and 0.036 ppm, corresponding to alkoxy-^<18>O- and carbonyl-^<18>O-labeled carbonyl carbons, in the ^<13>C-NMR spectrum. Doubly ^<18>O-labeled methyl benzoate showed an isotope shift of 0.050 ppm, equal to the sum of the two singly ^<18>O-labeled carbonyl carbons. Next, [1-^<13>C, 1,1,4-^<18>O_3]5-aminolevulinic acid (ALA) was fed to Arthrobacter hyalinus, and the resulting porphyrin was esterified with trimethyloxonium tetrafluoroborate to afford ^<13>C- and ^<18>O-labeled uroporphyrin III octamethyl ester. The ^<13>C-NMR signals exhibited carbonyl carbon ^<18>O-isotope shifts of 0.013,0.036 and 0.051 ppm, close to those obtained in the model experiment. Thus, the carbonyl oxygens of uroporphyrinogen III ang its oxidized product uroporpyrin III originated from ALA. This result shows that the loss of ^<18>O at the acetate carbonyls of the A-ring in vitamin B_<12> does not occur before the formation of uroporphyrinogen III.
社団法人日本薬学会の論文
1994-04-15