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Lysine 2,3-Aminomutase
- Source :
- Journal of Biological Chemistry; January 1989, Vol. 264 Issue: 3 p1357-1360, 4p
- Publication Year :
- 1989
-
Abstract
- The conversion of L-lysine to L-β-lysine is catalyzed by lysine 2,3-aminomutase. The reaction involves the interchange of the 2-amino group of lysine with a hydrogen at carbon 3. As such the reaction is formally analogous to adenosylcobalamin-dependent rearrangements. However, the enzyme does not contain and is not activated by this coenzyme. Instead it contains iron and pyridoxal phosphate and is activated by S-adenosylmethionine. Earlier experiments implicated adenosyl-C-5′ of S-adenosylmethionine in the hydrogen transfer mechanism, apparently in a role similar or analogous to that of adenosyl moiety of adenosylcobalamin in the B12-dependent rearrangements. The question of whether both hydrogens or only one hydrogen at adenosyl-C-5′ participate in the hydrogen-transfer process has been addressed by carrying out the lysine 2,3-aminomutase reaction with S-[5′-3H] adenosylmethionine in the presence of 10 times its molar concentration of enzyme. Under these conditions allof the tritium appeared in lysine and β-lysine, showing that C-5′-hydrogens participate. To determine whether hydrogen transfer is compulsorily intermolecular and intramolecular, various molar ratios of [3,3-2H2]lysine and unlabeled lysine were submitted to the action of lysine 2,3-aminomutase under conditions in which 10–15% conversion to β-lysine occurred. Mass spectral analysis of the β-lysine for monodeutero and dideutero species showed conclusively that hydrogen transfer is both intramolecular and intermolecular. The results quantitatively support our postulate that activation of the enzyme involves a transformation of S-adenosylmethionine into a form that promotes the generation of an adenosyl-5′ free radical, which abstracts hydrogen from lysine to form 5′-deoxyadenosine as an intermediate.
Details
- Language :
- English
- ISSN :
- 00219258 and 1083351X
- Volume :
- 264
- Issue :
- 3
- Database :
- Supplemental Index
- Journal :
- Journal of Biological Chemistry
- Publication Type :
- Periodical
- Accession number :
- ejs55939671
- Full Text :
- https://doi.org/10.1016/S0021-9258(18)94194-3