Evidence that the Fosfomycin-Producing Epoxidase, HppE, Is a Non-Heme-lron Peroxidase

摘要

The iron-dependent epoxidase HppE converts (5)-2-hydroxypropyl-l-phosphonate (S-HPP) to the antibiotic fosfomycin [(1R,2S)-epoxypropylphosphonate] in an unusual 1,3-dehydrogenation of a secondary alcohol to an epoxide. HppE has been classified as an oxidase, with proposed mechanisms differing primarily in the identity of the O_2-derived iron complex that abstracts hydrogen (H・) from C1 of S-HPP to initiate epoxide ring closure. We show here that the preferred cosubstrate is actually H_2O_2 and that HppE therefore almost certainly uses an iron(Ⅳ)-oxo complex as the H・ abstractor. Reaction with H_2O_2 is accelerated by bound substrate and produces fosfomycin catalytically with a stoichiometry of unity. The ability of catalase to suppress the HppE activity previously attributed to its direct utilization of O_2 implies that reduction of O_2 and utilization of the resultant H_2O_2 were actually operant.