Bio Remediation

A Quahog Enzyme With Potential For PCB Remediation

The development of a biomarker for marine organisms in the northeastern coastal region is of the utmost importance for tracking pollution levels and maintenance of the valuable shellfish crops. The biomarker is an enzyme, glutathione-S-transferase (GST), which is involved in the metabolism of xenobiotic compounds. The research aims include; selection of suitable organism(s) for study, purification of the enzyme and testing the idea that the enzyme will show a change in activity when in the presence of xenobiotic compounds such as polychlorinated biphenyls (PCBs). The shellfish chosen for enzyme extraction was the northern quahog Mercinaria mercinaria. The quahog was selected for experimentation because GST activity was determined to be higher in its tissues when compared with other bivalve mollusks. Quahog samples were collected from New Bedford Harbor, New Bedford MA and nonpolluted control sites where marine conditions were similar (e.g. Westport River, Westport MA). The samples were examined for protein content after purification by affinity chromatography. Biochemical characterization studies of quahog GST showed it to be an enzyme, which exists in multiple forms with molecular weights ranging from 24.5 to 27.3 kDa. The isoelectric points of the multiple subunits were between 4.8 and 5.1 thus placing quahog GST into the p class of GSTs. Initial rate kinetics experiments in the presence of Aroclor mixtures showed that increasing concentrations of PCBs have a direct effect on the GST activity. The characterization of quahog GST proved to have positive implications for the future of the enzyme as a biomarker and possibly for use in the dechlorination of PCBs.

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