Catalytic Water Oxidation by Iridium‐Modified Carbonic Anhydrase. Issue 3 (17th January 2018)

• Record Type: Journal Article
• Authors: Kim, Min‐Chul; Lee, Sang‐Yup
• Is Part Of: Chemistry, an Asian journal. Volume 13:Issue 3(2018)
• Page Start: 334
• Page End: 341
• Publication Date: 2018-01-17
• Subjects: iridium -- metalloenzymes -- oxygen -- oxidation -- water chemistry; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/asia.201701543
• Languages: English
• ISSNs: 1861-4728

Abstract

Abstract: Carbonic anhydrase (CA) is a ubiquitous metalloenzyme with a Zn cofactor coordinated to trigonal histidine imidazole moieties in a tetrahedral geometry. Removal of the Zn cofactor in CA and subsequent binding of Ir afforded CA[Ir]. Under mild and neutral conditions (30 °C, pH 7), CA[Ir] exhibited water‐oxidizing activity with a turnover frequency (TOF) of 39.8 min −1, which is comparable to those of other Ir‐based molecular catalysts. Coordination of Ir to the apoprotein of CA is thermodynamically preferred and is associated with an exothermic energy change (Δ H ) of −10.8 kcal mol −1, which implies that the CA apoprotein is stabilized by Ir binding. The catalytic oxygen‐evolving activity of CA[Ir] is displayed only if Ir is bound to CA, which functions as an effective biological scaffold that activates the Ir center for catalysis. The results of this study indicate that the histidine imidazoles at the CA active site could be exploited as beneficial biological ligands to provide unforeseen biochemical activity by coordination to a variety of transition‐metal ions. Abstract : Not a CA[Ir] in the world : Removal of the Zn cofactor in carbonic anhydrase (CA) and subsequent binding of Ir affords CA[Ir]. The CA apoprotein is stabilized by Ir binding, as confirmed by thermodynamics. Under mild and neutral conditions (30 °C, pH 7), CA[Ir] exhibits water‐oxidizing activity with a turnover frequency of 39.8 min −1 . This value is comparable to those of other Ir‐based molecular catalysts.