Characterization of the Microsomal Mixed -Function Oxidase System of Several Species of Sea Anemones (Phylum: Cnidaria).
Date of Award
Doctor of Philosophy (PhD)
Several studies have demonstrated detrimental effects of anthropogenic compounds on coral reef communities. These compounds are known to be bioaccumulated rapidly, but eliminated slowly by anthozoans (i.e., corals and sea anemones). The cytochrome P450-dependent mixed function oxidase (MFO) system is the primary pathway for initial oxidation of many hydrophobic exogenous compounds; however, its presence had not been well documented in anthozoans. The studies reported herein show that a functional cytochrome P450-dependent MFO is present in the microsomal fraction of the sea anemones Anthopleura xanthogrammica , A. elegantissima, and Bunodosoma cavernata . The evidence is based on the presence of classical microsomal MFO components (e.g., cytochrome P450 and flavin-containing reductases) and their ability to catalyze P450-dependent monooxygenase reactions (e.g., aldrin epoxidation and ethoxyresorufin O-dealkylation (EROD)) in the presence of NAD(P)H. The P450 specific contents and MFO activities are similar to values found in many other marine invertebrates. NADPH- and NADH-dependent EROD activity was consistently observed in A. elegantissima and A. xanthogrammica; however, it was below the detection limit of the assay for B. cavernata. In contrast, NADPH- and NADH-dependent aldrin epoxidation activity was consistently observed in B. cavernata and A. elegantissima, but it was less consistently observed in A. xanthogrammica. Despite the much higher NADH-cytochrome c and ferricyanide reductase activities, sea anemone monooxygenase reactions consistently preferred NADPH as a cofactor for EROD. The aldrin epoxidation activity tended to be slightly higher with NADPH versus NADH; however, there were a few preparations that strongly preferred either NADH or NADPH. The difference in preference of electron donors between microsomal preparations may result from differential expression of P450 isoforms capable of metabolizing aldrin. Further, the presence of multiple microsomal P450 isoforms in these sea anemones was indicated by immunodetection. Several antibodies raised against rat or fish P450 isoforms of the CYP 1, 2, and 3 families recognized protein(s) between 50--60 KDa in the microsomal fraction of each species studied that were characteristic of P450. Anti-CYP2K also recognized a 40 KDa protein that was not characteristic of P450.
Heffernan, Linda Marie, "Characterization of the Microsomal Mixed -Function Oxidase System of Several Species of Sea Anemones (Phylum: Cnidaria)." (1999). LSU Historical Dissertations and Theses. 7046.