Microorganisms were screened for their ability to release cadmium from scallop hepatopancreas, which is the main residue after removing of the edible parts of scallop. The isolated strain, 23-0-11, identified as Arthrobacter nicotinovorans, secreted a protease which released cadmium from scallop hepatopancreas into the liquid medium. The molecular mass of the enzyme was estimated to be 27 kDa. The sequence of the 15 N-terminal amino acids of the protease showed no close similarity with any other protein. Compared with a commercial enzyme, the purified protease had greater ability to release cadmium. The enzyme activity was greatest at 50 degrees C and pH 7.0, and was enhanced in the presence of Ca(2+), Mg(2+) and Mn(2+), while being strongly inhibited by Co(2+). The inhibition profile by the serine protease inhibitor, phenylmethylsulphonyl fluoride (PMSF), confirmed that the protease belonged to the serine protease family.