Applications of Density Functional Theory to Biological and Bioinorganic Chemistry by Mihai V. Putz & D. Michael P. Mingos

Author:Mihai V. Putz & D. Michael P. Mingos
Language: eng
Format: epub
Publisher: Springer Berlin Heidelberg, Berlin, Heidelberg

3.2 Nitrite and Nitrate

Nitrite binding to metals is well known in traditional inorganic chemistry as an example of linkage isomerism—occurring either via the nitrogen or via the oxygen atom, cf. Fig. 5. In the past few years it has been recognized that the same linkage isomerism is also at work in metalloproteins [30, 52–56]. An initial DFT prediction was made despite a wealth of experimental data showing nitrite binding to hemoproteins only via its nitrogen atom, binding via the oxygen should also be possible [30]. Soon afterwards, the crystal structures of nitrite-bound myoglobin and hemoglobin were reported, showing indeed the DFT-predicted isomer [52–56]. Subsequent detailed studies, with DFT, ab initio dynamics, and QM/MM approaches [57] have also revealed that nitrite reduction is almost equally feasible via the two isomers, suggesting perhaps one more case of mechanistic promiscuity, as illustrated in Fig. 5 [57]. Also based on DFT data, linkage isomerism was proposed to be feasible in copper-containing nitrite reductases [58], as well as in molybdenum-containing nitrate reductases—as the latter enzymes can reduce nitrite at competition with nitrate [32]. In the case of nitrate reductase, nitrate and nitrite were computed to be reducible at very similar rates [32].

Fig. 5Nitrite linkage isomerism and reduction at hemoprotein active sites

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