Metalloenzymes use metal atoms to augment their catalytic range and power. Recent structural determinations of enzymes involved in the metabolism of small molecules (such as dinitrogen and molecular hydrogen) have revealed clusters of asymmetrically arranged metal atoms, and some progress has been made in identifying the proteins that sequester and deliver the constituent transition metals (such as Mo and Ni). The Fe atom in bacterial [NiFe]-hydrogenase is coordinated by CO and CN- ligands, and the genesis of these rather toxic moieties has been mysterious. Paschos et al. show that in vitro HypF catalyzes the hydrolysis of carbamoyl phosphate as well as the carbamoyl phosphate-dependent release of pyrophosphate from ATP. They suggest that in vivo HypF catalyzes adenylation at the oxygen of the tautomeric form of the carbamoyl group; subsequent abstraction of the hydrogen atom from the imino nitrogen would yield the cyano group. Rosano et al. have determined the structure of the HypF acylphosphatase domain, which may initiate this reaction by removing the phosphate and attaching the carbamoyl group to an amino acid residue in a tautomer-favoring environment. -- GJC
J. Biol. Chem. 10.1074/jbc.M204601200 (2002); J. Mol. Biol. 321, 785 (2002).
