Special Issue on Nitrogenases and Homologous Systems

Abstract

The nitrogenase superfamily comprises homologous enzyme systems that carry out fundamentally important processes, including the reduction of N2 and CO, and the biosynthesis of bacteriochlorophyll and coenzyme F430. This special issue provides a cross‐disciplinary overview of the ongoing research in this highly diverse and unique research area of metalloprotein biochemistry.

Photochemistry and photoinhibition of the H-cluster of FeFe hydrogenases

“…H 2 is also a byproduct of the reduction of N 2 to NH 3 , a key step in the global nitrogen cycle which occurs e.g. in cyanobacteria: the latter reaction is catalyzed by the enzyme nitrogenase, which evolves at least one molecule of H 2 per N 2 reduced 4,5 .…”

Nitrogenase Chemistry at 10 Kelvin─Phototautomerization and Recombination of CO-Inhibited α-H195Q Enzyme

“…1,4 The other half of worldwide NF is accomplished by some prokaryotic bacteria and archaea, known as diazotrophs, using the enzyme nitrogenase (N 2 ase). 5,6 The best-studied, most efficient N 2 ase (Mo−N 2 ase) uses a MoFe 7 S 9 C-homocitrate cluster, called the FeMo-cofactor 7 (Figure 1), as its site for substrate binding and reduction. 8−11 The reduction of N 2 to NH 3 is driven by ATP hydrolysis and accompanied by the evolution of H 2 : N 2 + 8H + + 8e − + 16ATP → 2NH 3 + H 2 + 16ADP + 16Pi.…”

“…Nowadays, about 50% of NF occurs via the industrial Haber–Bosch (HB) process, using Fe-based catalysts, high temperatures (∼700 K), and high pressures (>100 bar) . The HB process, now over 100 years old, is often considered the most influential factor in human-population growth, but it costs nearly 2% of world-energy production and has environmental downsides, such as CO 2 emissions from H 2 production and eutrophication from agricultural runoff. , The other half of worldwide NF is accomplished by some prokaryotic bacteria and archaea, known as diazotrophs, using the enzyme nitrogenase (N 2 ase). , …”

Nitrogenase Fe Protein: A Multi-Tasking Player in Substrate Reduction and Metallocluster Assembly

“…Three homologous nitrogenases, designated the Mo-, V-, and Fe-only nitrogenases [ 5 , 6 ], have been identified to date, which is mainly distinguished by the presence or absence of a heterometal at their respective cofactor sites. Encoded by nif genes, the “conventional” Mo-nitrogenase from Azotobacter vinelandii is the best-characterized member of this enzyme family, which consists of two components.…”

“…The “alternative” V- and Fe-only nitrogenases, like their Mo-counterpart, use two-component systems to effect substrate reduction. Encoded by vnf and anf genes, respectively, the component proteins of the V- and Fe-only nitrogenases share a good degree of sequence and structural homology with their respective counterparts in the Mo-nitrogenase; in particular, the Fe protein components of the three nitrogenases, encoded by nifH , vnfH and anfH , respectively, are highly similar in structure and function despite displaying distinct features on their own [ 5 , 6 ].…”