Sacrificial Cobalt-Carbon Bond Homolysis in Coenzyme B12as a Cofactor Conservation Strategy.Campanello, G.C., Ruetz, M., Dodge, G.J., Gouda, H., Gupta, A., Twahir, U.T., Killian, M.M., Watkins, D., Rosenblatt, D.S., Brunold, T.C., Warncke, K., Smith, J.L., Banerjee, R.
(2018) J. Am. Chem. Soc. 140: 13205-13208
- PubMed: 30282455
- DOI: 10.1021/jacs.8b08659
- Primary Citation of Related Structures:
- PubMed Abstract:
A sophisticated intracellular trafficking pathway in humans is used to tailor vitamin B <sub>12 </sub> into its active cofactor forms, and to deliver it to two known B <sub>12 </sub>-dependent enzymes. Herein, we report an unexpected strategy for cel ...
A sophisticated intracellular trafficking pathway in humans is used to tailor vitamin B 12 into its active cofactor forms, and to deliver it to two known B 12 -dependent enzymes. Herein, we report an unexpected strategy for cellular retention of B 12 , an essential and reactive cofactor. If methylmalonyl-CoA mutase is unavailable to accept the coenzyme B 12 product of adenosyltransferase, the latter catalyzes homolytic scission of the cobalt-carbon bond in an unconventional reversal of the nucleophilic displacement reaction that was used to make it. The resulting homolysis product binds more tightly to adenosyltransferase than does coenzyme B 12 , facilitating cofactor retention. We have trapped, and characterized spectroscopically, an intermediate in which the cobalt-carbon bond is weakened prior to being broken. The physiological relevance of this sacrificial catalytic activity for cofactor retention is supported by the significantly lower coenzyme B 12 concentration in patients with dysfunctional methylmalonyl-CoA mutase but normal adenosyltransferase activity.
Department of Biological Chemistry , University of Michigan , Ann Arbor , Michigan 48109-0600 , United States.,Life Sciences Institute, University of Michigan , Ann Arbor , Michigan 48109-0600 , United States.,Department of Physics , Emory University , Atlanta , Georgia 30322-2430 , United States.,Department of Chemistry , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States.,Indian Institute of Science Education and Research , Pune 411008 , India.,Department of Human Genetics , McGill University , Montreal , Quebec H3A 1B1 , Canada.