Exploring the role of chitinolytic enzymes in the sea fan coral, <Emphasis Type="Italic">Gorgonia ventalina</Emphasis>

Chitinases are involved in defense against chitinaceous pathogens in both invertebrates and vertebrates. This study investigated whether sea fan corals, Gorgonia ventalina (Linnaeus) collected from the Florida Keys between the summer of 2002 and the summer of 2005 contain chitinases, and whether these enzymes could serve an analogous protective role against the fungal pathogen, Aspergillus sydowii (Thom et Church). Crude extracts of healthy sea fans contained detectible levels of exochitinase activity in an in vitro microplate assay using fluorogenic substrates. The exochitinase levels decreased upon injury, agitation, or manipulation of the tissue. A concurrent, transient increase of exochitinase in the surrounding water suggests that sea fans release chitinases as a response to these stresses. By contrast, endochitinase was detected in only 2 of 15 sea fans (13%), suggesting a high degree of variation for this enzyme. Sea fan chitinase-containing seawater and anion exchange chromatography fractions were both active against A. sydowii in an absorbance-based antifungal assay. The presence of chitinases in sea fan extracts, their release into the surrounding water upon stress, and their activity against A. sydowii suggests that further study of these enzymes in coral stress responses is warranted.