Substrate-triggered addition of dioxygen to the diferrous cofactor of aldehyde-deformylating oxygenase to form a diferric-peroxide intermediate

Maria E. Pandelia, Ning Li, Hanne Nørgaard, Douglas M. Warui, Lauren J. Rajakovich, Wei Chen Chang, Squire J. Booker, Carsten Krebs, J. Martin Bollinger

Research output: Contribution to journalArticlepeer-review

51 Scopus citations

Abstract

Cyanobacterial aldehyde-deformylating oxygenases (ADOs) belong to the ferritin-like diiron-carboxylate superfamily of dioxygen-activating proteins. They catalyze conversion of saturated or monounsaturated Cn fatty aldehydes to formate and the corresponding Cn-1 alkanes or alkenes, respectively. This unusual, apparently redox-neutral transformation actually requires four electrons per turnover to reduce the O2 cosubstrate to the oxidation state of water and incorporates one O-atom from O2 into the formate coproduct. We show here that the complex of the diiron(II/II) form of ADO from Nostoc punctiforme (Np) with an aldehyde substrate reacts with O2 to form a colored intermediate with spectroscopic properties suggestive of a Fe2III/III complex with a bound peroxide. Its Mössbauer spectra reveal that the intermediate possesses an antiferromagnetically (AF) coupled Fe2III/III center with resolved subsites. The intermediate is long-lived in the absence of a reducing system, decaying slowly (t1/2 ∼ 400 s at 5 C) to produce a very modest yield of formate (<0.15 enzyme equivalents), but reacts rapidly with the fully reduced form of 1-methoxy-5-methylphenazinium methylsulfate ( MeOPMS) to yield product, albeit at only ∼50% of the maximum theoretical yield (owing to competition from one or more unproductive pathway). The results represent the most definitive evidence to date that ADO can use a diiron cofactor (rather than a homo- or heterodinuclear cluster involving another transition metal) and provide support for a mechanism involving attack on the carbonyl of the bound substrate by the reduced O2 moiety to form a Fe2III/III-peroxyhemiacetal complex, which undergoes reductive O-O-bond cleavage, leading to C1-C2 radical fragmentation and formation of the alk(a/e)ne and formate products.

Original languageEnglish (US)
Pages (from-to)15801-15812
Number of pages12
JournalJournal of the American Chemical Society
Volume135
Issue number42
DOIs
StatePublished - Oct 23 2013

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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