title: Kinetic studies on the reaction of cob(II)alamin with hypochlorous acid: Evidence for one electron oxidation of the metal center and corrin ring destruction.
abstract: Kinetic and mechanistic studies on the reaction of a major intracellular vitamin B12form, cob(II)alamin (Cbl(II)), with hypochlorous acid/hypochlorite (HOCl/OCl-) have been carried out. Cbl(II) (Co(II)) is rapidly oxidized by HOCl to predominately aquacobalamin/hydroxycobalamin (Cbl(III), Co(III)) with a second-order rate constant of 2.4×107M-1s-1(25.0°C). The stoichiometry of the reaction is 1:1. UHPLC/HRMS analysis of the product mixture of the reaction of Cbl(II) with 0.9mol equiv. HOCl provides support for HOCl being initially reduced to Cl and subsequent H atom abstraction from the corrin macrocycle occurring, resulting in small amounts of corrinoid species with two or four H atoms fewer than the parent cobalamin. Upon the addition of excess (H)OCl further slower reactions are observed. Finally, SDS-PAGE experiments show that HOCl-induced damage to bovine serum albumin does not occur in the presence of Cbl(II), providing support for Cbl(II) being an efficient HOCl trapping agent.
authors: Department of Chemistry and Biochemistry, Kent State University, Kent, OH 44242, USA.
authors: Rohan S
authors: RS
authors: Dassanayake
authors: Department of Chemistry and Biochemistry, Kent State University, Kent, OH 44242, USA.
authors: Mohamed M
authors: MM
authors: Farhath
authors: Department of Chemistry and Biochemistry, Kent State University, Kent, OH 44242, USA.
authors: Jacob T
authors: JT
authors: Shelley
authors: Department of Chemistry and Biochemistry, Kent State University, Kent, OH 44242, USA.
authors: Soumitra
authors: S
authors: Basu
authors: School of Applied Sciences, Auckland University of Technology, Private Bag 92006, Auckland 1142, New Zealand. Electronic address: nbrasch@aut.ac.nz.
authors: Nicola E
authors: NE
authors: Brasch
mesh_terms: D000818:Animals; D002417:Cattle; D004583:Electrons; D006997:Hypochlorous Acid / Q000737:chemistry*; D007700:Kinetics; D010084:Oxidation-Reduction; D012710:Serum Albumin, Bovine / Q000737:chemistry; D014805:Vitamin B 12 / Q000737:chemistry*
chemical_list: D012710:Serum Albumin, Bovine; D006997:Hypochlorous Acid; D014805:Vitamin B 12
keywords: Cobalamins; Corrin ring destruction; Hypochlorous acid, kinetics; Vitamin B(12)