The distribution of zinc in the oyster Ostrea edulis and its relation to enzymic activity and to other metals

The role of zinc in the oyster Ostrea edulisLinnaeus has been studied in its relation to the zinc-dependent enzymes present and in relation to the copper, calcium, magnesium, sodium, potassium and phosphate contents. Only carbonic anhydrase, alkaline phosphatase, carboxypeptidase A and malic dehydrogenase zinc metalloenzyme activities could be detected. -D-mannosidase, a zinc-dependent enzyme hitherto not reported for the oyster, was also detected. After tissue dissection into muscle, palps, gills, mantle and digestive mass and subcellular fractionation of these tissues, analysis indicated that no single tissue concentrates zinc or the zinc-dependent enzymes. The total amount of zinc found is far in excess of the amount of zinc contributed by the zinc-dependent enzymes, but the amount of non-dialysable zinc is of the same order of magnitude. It is suggested that this apparent excess of dialysable zinc is a consequence of the high levels of calcium found in the tissues, demonstrating a competition between calcium and zinc in their uptake, as is well documented in many other phyla.