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Mechanism of Perfluoroalkyl Halide Toxicity: Catalysis of Perfluoroalkylation by Reduced Forms of Cobalamin (Vitamin B12)

N. V. Beda* and A. A. Nedospasov

Institute of Molecular Genetics, Russian Academy of Sciences, pl. Kurchatova 2, Moscow 123182, Russia; E-mail: beda@img.ras.ru

* To whom correspondence should be addressed.

Received May 23, 2003; Revision received August 5, 2003
Perfluoroalkyl halides (PFHs) are synthetic products widely used in various fields. Perfluorooctyl bromide (PFB) is used in medicine as a component of blood substitutes and for artificial lung ventilation. In both cases, it is considered a completely inert compound acting as a solvent for oxygen. However, there are many reports of PFH-induced intoxication, including lethal cases. Mechanisms underlying toxic effects of this compound remain unknown. In this study, we demonstrate that the reduced form of cobalamin (vitamin B12) typical for B12-dependent enzymes can catalyze the reactions of perfluoroalkylation, aromatic substitution, or addition by double bonds. Synthesis of perfluoro derivatives from PFHs during catalysis by cob(I)alamin-like super nucleophiles is a new possible mechanism responsible for in vivo formation of highly toxic compounds from “chemically inert” substances widely used in medicine. Catalytic perfluoroalkylation might possibly contribute to nitric oxide depletion and modulation of activity of guanylate cyclase, cytochromes, NO-synthases, and other heme-containing proteins.
KEY WORDS: vitamin B12, heme, guanylate cyclase, cobalamin, perfluorooctyl bromide, perfluoroalkyl halides, perfluorocarbons, Perftoran, cytochrome, Freon, cytotoxicity, NO-synthases, Perflubron