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AN ENZYME that contains cadmium could explain the puzzling distribution of
the heavy metal in the oceans, say researchers in New Jersey. Cadmium is
extremely toxic, but its distribution in seawater resembles that of a nutrient,
suggesting that it has some biological use. Prompted by this riddle, Todd Land
and François Morel of Princeton University found a marine alga that uses
cadmium to make an enzyme for mopping up carbon from seawater (Proceedings
of the National Academy of Sciences, vol 97, p 4627). The catalytic cores
of enzymes are often metallic, but this is the first time that cadmium has been
found in the core of an enzyme, says Lane.