ABSTRACT
To clarify the origin of amide-nitrogen of vitamin B12, [1-13C]aminolevulinic acid (ALA) and L-[amide-15N]glutamine were administered to P. shermanii. The 13C-nuclear magnetic resonance spectrum of the vitamin B12 subsequently isolated showed distinct 13C-15N coupling and isotope shift at six amide carbons. However, the C-57 amide carbon showed neither coupling, nor shift. Thus, it was concluded that the nitrogens of 6 amides of the side chain were derived from glutamine and the C-57 amide nitrogen was from threonine.
Subject(s)
Porphyrins/biosynthesis , Vitamin B 12/biosynthesis , Corrinoids , Magnetic Resonance Spectroscopy/methods , Nitrogen IsotopesABSTRACT
To clarify the origin of nitrogen of vitamin B12, 15N-labeled aminolevulinic acid (ALA) was prepared and administered to Propionibacterium shermanii. Vitamin B12 thus isolated showed four signals in the nitrogen-15 nuclear magnetic resonance (15N-NMR) spectrum. The nitrogen of [5-15N]riboflavine was incorporated into the benzimidazole part of vitamin B12. Hydroxycobalamin was transformed into cyanocobalamin by treatment with [15N]potassium cyanide, and the 15N-NMR spectrum was measured. The results of these experiments revealed the origin of the nitrogen atoms of vitamin B12, and allowed the 15N-NMR signals to be assigned.
Subject(s)
Nitrogen/metabolism , Propionibacterium/metabolism , Vitamin B 12/biosynthesis , Chemical Phenomena , ChemistryABSTRACT
The oxidation of tyrosine by monophenol monooxygenase (tyrosinase: EC 1.10.3.1) to melanin has been studied by a combination of ultraviolet, circular dichroism, and nuclear magnetic resonance techniques. It is demonstrated that the chiral intermediate (dopachrome) is generated stereoselectively in this enzymic reaction.
Subject(s)
Catechol Oxidase/metabolism , Melanins/biosynthesis , Chemical Phenomena , Chemistry , Circular Dichroism , Magnetic Resonance Spectroscopy , Molecular Conformation , Spectrophotometry, UltravioletABSTRACT
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.
