1 Biochemical aspects of

It has been found in some places around New Zealand, specifically in Tasman Bay, Foveaux Strait and Chatham islands, that the concentration of cadmium (Cd) in the Bluff oyster (Ostrea chilensis) is very high, and similar to that of oysters from polluted areas. This is unexpected because both water and sediments are very clean in these places, and the environmental concentration of Cd is very low. Cadmium is a hazardous heavy metal classified by the World Health Organisation within the group 1 (Human Carcinogens) and listed by the Comprehensive Environmental Response, Compensation, and Liability Act as being No7 in its list of hazardous materials. However, epidemiological studies undertaken in people consuming Bluff oysters proved no sign of Cd-intoxication which could imply that the cadmium is not free in the oyster, but protein bound. At present, it is unknown which protein might be responsible for the binding of Cd in the Bluff oyster. This study aimed to develop a procedure to localize and identify the Cd-binding protein (Cd-BP) in the Bluff oyster. A combination of gel filtration chromatography (GFC) to separate the proteins of the Bluff oyster, and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to analyse the metal content of the fractions, proved to be the most reliable procedure and resulted in the isolation of one candidate Cd-BP. Further analysis using MALDI MS/MS and a de novo sequencing of the candidate identified the hypothetical protein PPAM2_20180 (Pseudomonas sp.). The present study has also contributed to the data available on the distribution of selected trace metals between the soluble and insoluble fractions in oyster tissue, and made a new contribution to the literature by showing the distribution of metals among the high molecular weight proteins (30 – 600 kDa) of the soluble fraction of the Bluff oyster tissue