Other Metals 

In the human body in terms of abundance, zinc is the most significant trace element after iron. Like it takes place only as Zn²⁺ it is not redox active, although coordination of molecules to the 'soft' cation is involved in several enzymes for acid catalysis. These involve carbonic anhydrase, that converts HCO₃^- to CO₂, and enzymes for condensation and hydrolysis reactions of biopolymers. Zinc-containing proteins as well carry out regulatory functions; for instance, zinc finger proteins recognize particular DNA sequences and are included in gene function.

Nitrogen fixation is performed through specialized microorganisms that reduce atmospheric N₂ to biological nitrogen compounds. General nitrogenase enzymes consist of molybdenum and iron, but less general forms with vanadium are known.

Part of the cobalt-containing coenzyme B₁₂ is diaplayed in diagram 1d. The group X is variable; X=CH₃ provides methyl cobalamin that appears to be the only biological compound consisting of an organometallic metal-carbon bond. It carries out alkylations and radical-induced rearrangements of biological compounds.