Nickel enzymes, present in archaea, bacteria, plants, and primitive eukaryotes are divided into redox and nonredox enzymes and play key functions in diverse metabolic processes, such as energy metabolism and virulence. They catalyze various reactions by using active sites of diverse complexities, such as mononuclear nickel in Ni‐superoxide dismutase, glyoxylase I and acireductone dioxygenase, dinuclear nickel in urease, heteronuclear metalloclusters in [NiFe]‐carbon monoxide dehydrogenase, acetyl‐CoA decarbonylase/synthase and [NiFe]‐hydrogenase, and even more complex cofactors in methyl‐CoM reductase and lactate racemase. The presence of metalloenzymes in a cell necessitates a tight regulation of metal homeostasis, in order to maintain the appropriate intracellular concentration of nickel while avoiding its toxicity. As well, the biosynthesis and insertion of nickel active sites often require specific and elaborated maturation pathways, allowing the correct metal to be delivered and incorporated into the target enzyme. In this review, the phylogenetic distribution of nickel enzymes will be briefly described. Their tridimensional structures as well as the complexity of their active sites will be discussed. In view of the latest findings on these enzymes, a special focus will be put on the biosynthesis of their active sites and nickel activation of apo‐enzymes.

Among the possible renewable energies sources, biomass gasification has been considered one promising alternative to meet the daily growing energy demand. The outcome of this process is a synthetic gas (syngas) mainly composed of carbon monoxide and hydrogen. Syngas can be upgraded by a group of anaerobic micro-organisms, thanks to the biologically mediated water–gas shift (WGS) reaction. In this process, the conversion of CO and H₂O into CO₂ and H₂ is catalyzed by two enzymes: carbon monoxide dehydrogenase (CODH) and hydrogenase. In order to efficiently use micro-organisms as a cost effective and environmentally friendly technology, it is fundamental to deeply understand how this process occurs. In this review paper, an overview on the possible biotechnological uses of the WGS reaction is presented, focusing mainly on the fundamental characterization of the CODH enzyme.

Staphylococcus aureuspossesses two canonical ABC-importers dedicated to nickel acquisition: the NikABCDE and the CntABCDF systems, active under different growth conditions.