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Diseases of Aquatic Organisms

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DAO 67:225-231 (2005)  -  doi:10.3354/dao067225

Identification and partial characterisation of metalloproteases secreted by a Mesanophrys-like ciliate parasite of the Norway lobster Nephrops norvegicus

H. J. Small1,3,*, D. M. Neil1, A. C. Taylor1, G. H. Coombs2

1Division of Environmental and Evolutionary Biology, and 2Division of Infection and Immunity, Institute of Biomedical & Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
3Present address: Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, Virginia 23062, USA

ABSTRACT: A ciliate parasite, tentatively identified as Mesanophrys sp. of Norway lobsters Nephrops norvegicus, is demonstrated to secrete several proteases into the culture medium (modified Nephrops saline). Analyses using substrate-impregnated sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed 12 activity bands differing greatly in mobility in the gels. The complete inhibition of proteolytic activity by 1,10-phenanthroline indicated that the proteases are of the metallo class. The proteases were active at the physiological temperature (8°C) and haemolymph pH (7.8) of the host. The proteases were selective in the degradation of several host proteins, including the myosin heavy chain, which is a major structural component of lobster muscle. Consequently, these proteases may have important roles in several aspects of the host–parasite interaction including invasion, nutrient uptake by the ciliate, and pathogenesis.

KEY WORDS: Ciliate · Parasite · Proteases · Secreted · Pathology

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