Studies on the biosynthesis of corrinoids and porphyrinoids. I. The labeling of oxygen of vitamin B12.
Recently the amide-oxygen has been suggested to participate in the formation of the corrin ring of vitamin B12. To confirm this hypothesis, 17O-labeled aminolevulinic acid (ALA) was prepared and administered to Propionibacterium shermanii. The isolated vitamin B12 showed only broad 17O signals in the oxygen-17 nuclear magnetic resonance (17O-NMR) spectrum. However, distinct isotope-shifted peaks were observed in the 13C-NMR spectrum of vitamin B12 isolated after incorporation of [1-13C:1,4-18O2]ALA. Of these shifted peaks, one peak (C27) showed very low intensity. This indicates that dilution of 18O occurred at the acetyl chain of the A ring of vitamin B12. This result supports the assumption that the lactone formation of the A ring promotes the ring contraction, as proposed by Eschenmoser.
Kurumaya
K
K
Okazaki
T
T
Kajiwara
M
M
D045728:Corrinoids; D010103:Oxygen Isotopes; D011166:Porphyrins / Q000096:biosynthesis*; D011424:Propionibacterium / Q000378:metabolism; D014805:Vitamin B 12 / Q000096:biosynthesis*
D045728:Corrinoids; D010103:Oxygen Isotopes; D011166:Porphyrins; D014805:Vitamin B 12