The Structure of the Hyponitrite Species in a Heme FeCu Binuclear Center

✍ Scribed by Constantinos Varotsis; Takehiro Ohta; Teizo Kitagawa; Tewfik Soulimane; Eftychia Pinakoulaki

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 194 KB
• Volume: 119
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/ange.200602963

✦ Synopsis

The formation of the hyponitrite species from two NO molecules is the key intermediate in the reduction of NO to N 2 O in denitrification. [1] The reaction is used by bacteria as an alternative to oxygen-based respiration. [1,2] The bacterial nitric oxide reductase (Nor) and the ba 3 -oxidoreductase from Thermus thermophilus catalyze the reaction: 2 NO + 2 e À + 2 H + !N 2 O + H 2 O. [2] The latter enzyme contains a homodinuclear copper complex (Cu A ), one low-spin, sixcoordinate heme b, and a binuclear center that consists of Cu B and a high-spin heme a 3 in which the catalytic reactions take place. [3] A full elucidation of the structure and the electronic configuration of various intermediates are of profound importance for understanding the mechanism by which the enzymes form and cleave the N À N and N À O bonds, respectively. The mechanisms of the reduction of NO to N 2 O by both Nor and ba 3 -oxidoreductase are poorly understood because of the lack of detection of the short-lived intermediate species. [4,5] However, a six-coordinate heme