7dvo

Publication Abstract from PubMed

Nitric oxide (NO) reductase from the fungus Fusarium oxysporum is a P450-type enzyme (P450nor) that catalyzes the reduction of NO to nitrous oxide (N2O) in the global nitrogen cycle. In this enzymatic reaction, the heme-bound NO is activated by the direct hydride transfer from NADH to generate a short-lived intermediate ( I ), a key state to promote N-N bond formation and N-O bond cleavage. This study applied time-resolved (TR) techniques in conjunction with photolabile-caged NO to gain direct experimental results for the characterization of the coordination and electronic structures of I TR freeze-trap crystallography using an X-ray free electron laser (XFEL) reveals highly bent Fe-NO coordination in I , with an elongated Fe-NO bond length (Fe-NO = 1.91 A, Fe-N-O = 138 degrees ) in the absence of NAD(+) TR-infrared (IR) spectroscopy detects the formation of I with an N-O stretching frequency of 1,290 cm(-1) upon hydride transfer from NADH to the Fe(3+)-NO enzyme via the dissociation of NAD(+) from a transient state, with an N-O stretching of 1,330 cm(-1) and a lifetime of ca. 16 ms. Quantum mechanics/molecular mechanics calculations, based on these crystallographic and IR spectroscopic results, demonstrate that the electronic structure of I is characterized by a singly protonated Fe(3+)-NHO(*-) radical. The current findings provide conclusive evidence for the N2O generation mechanism via a radical-radical coupling of the heme nitroxyl complex with the second NO molecule.

Short-lived intermediate in N2O generation by P450 NO reductase captured by time-resolved IR spectroscopy and XFEL crystallography.,Nomura T, Kimura T, Kanematsu Y, Yamada D, Yamashita K, Hirata K, Ueno G, Murakami H, Hisano T, Yamagiwa R, Takeda H, Gopalasingam C, Kousaka R, Yanagisawa S, Shoji O, Kumasaka T, Yamamoto M, Takano Y, Sugimoto H, Tosha T, Kubo M, Shiro Y Proc Natl Acad Sci U S A. 2021 May 25;118(21). pii: 2101481118. doi:, 10.1073/pnas.2101481118. PMID:34001620^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.