A LOBSTER CYSTEINE PROTEASE WITH IMMUNOREACTIVITY AND ACTIVITIES OF CALCITONIN AND CGRP

The high concentrations of molecules immunologically related to salmon calcitonin (CT) and/or to human calcitonin gene-related peptide (CGRP ) in the oesophagus of the norway lobster Nephrops norvegicus have bee n examined In the present study, we report the purification of these m olecules by means of a specific radioimmunoassay for calcitonin and ca lcitonin gene related peptide. The immunoreactive molecules were teste d for their functional similarities with CT and CGRP. This was investi gated by measuring their ability to interact with CGRP and CT radiorec eptor assays and to stimulate the adenylate cyclase activity in rat li ver and kidney membranes, respectively. In addition, the purified prod uct was injected in young rats in order to check for a CT-like biologi cal activity of these molecules. The combination of these tests led us to purify a molecular form of 33 kDa. N-terminal sequence analysis of this protein revealed a considerable homology with the lobster cystei ne proteases and the human cathepsin L. Control experiments performed with the highly purified American lobster cysteine protease 1 showed t hat crustacean cysteine proteases given in vivo to rats induce a fall in the plasma calcium and phosphate levels. This study therefore adds further documentation for a common ancestral origin of CT, CGRP and th e much larger cysteine proteases from invertebrates.