Cobalt prokaryotes

There was a primitive separation between organisms heavily dependent on iron, nickel (especially) and cobalt, the archebacteria, and other prokaryotes where the dominance of iron is more obvious. 

Finally, we must somehow resolve the vexing problem of the chemical speciation of trace elements in seawater what is the chemical nature of the various metal chelators whose existence has been demonstrated by electrochemistry Is the chemistry of several metals in surface seawater really controlled by metallophores released by prokaryotes Or are dissolved metals chiefly present as parts of metalloproteins in the process of remineralization How do metal chelators affect the residence times of metals (in particular, scavenged elements such as iron and cobalt) and in turn how do those chelators influence the global carbon cycle via changes in marine primary productivity ... 

With this cautionary note in mind, we should note that a related enzyme, prolidase from P. furiosus, has also been reported to be a dicobalt enzyme. In contrast to the aminopeptidases discussed above, prolidase specifically cleaves dipeptides containing a C-terminal proline. Prolidase is present in humans and a variety of bacteria, and appears to be identical to the enzyme previously known as organophosphorus acid anhydrolase, which can hydrolyze and detoxify organophosphorus nerve agents.A function in hydrolyzing peptides, rather than nerve agents that have only been known for a few decades, seems much more probable for these enzymes, which are found in both eukaryotes and prokaryotes. Whether prolidases actually utilize a dinuclear cobalt site in catalysis will require further investigation. 

The metal dependence of ribonucleotide reductase is cobalt as vitamin Bi2 (prokaryotes) and iron (eukaryotes), with some evidence for manganese as cofactor [66]. The reader is referred to Ref. [66] for a recent discussion on the mechanism of these interesting enzymes. In essence, the reaction can be described ... 

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