Biochemical analysis of the enzymatic complex responsible for the generation of superoxide anion on the cell surface of Chattonella marina

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Chattonella. marina (C. marina), a raphidophycean flagellate, is one of the most noxious, red tide phytoplankton, and is highly toxic to fish, especially to yellowtail Seriola quinquer adiata. Previous our studies have demonstrated that a decrease in.oxygen partial pressure of arterial blood is the earliest physiological disturbance observed in fish after exposure to C. marina. Physiological and histological studies of fish exposed to C. marina also suggested that the blockade of respiratory water flow through the gill lamellae caused by excessive mucus interferes with oxygen transfer, resulting in asphyxia. One of the biochemical feature of C, marina is the ability to generate reactive oxygen species (ROS) such as superoxide anion and hydrogen peroxide. In this study, we analyzed the enzymatic complex. responsible for the production of ROS, which may be located on the cell-surface of C. marina. Our results suggest that glycocalyx may include ROS generating enzymatic system. Glycocalyx is a complex structure consisted of carbohydrates and proteins, and is easily discharged from C. marin cells in responding to various physical stimuli. In fact, our immunohistochemical analysis using anti-serum against glycocalyx revealed that significant amounts of glycocalyx were attached on the gill surface of yellowtail after C. marina exposure. Furthermore, we found that crude glycocalyx prepared from C. marina cell suspension produces ROS in the presence of NADPH. These findings suggest that glycocalyx may play a important role in the ROS-mediated fish-killing mechanism of C. marina. In addit ion to ROS, our recent study suggest that C. marina contains photoactive hemolytic toxin as a novel toxic factor. Further studies are required to clarify the involvement of such he molytic toxin in the fish-killing mechanism of C. marina.