Isolation and characterization of monoclonal antibodies against calcium-activated neutral protease with low calcium sensitivity.

Fifteen hybridomas secreting antibodies against calcium-activated neutral protease (CANP), especially those for rabbit muscle mCANP with low calcium sensitivity, have been produced by the cell fusion technique. Eight of the monoclonal antibodies belong to the class IgG1, one to the class IgG2a, and six to the class IgG2b. The antibodies from these clones were characterized with regard to their relative binding affinities to the large subunits (80K) and the small subunits (30K) of mCANP as well as mu CANP, which is another type of CANP with high calcium sensitivity. Fourteen antibodies bound only to the 80K subunit of mCANP and one antibody bound to the 80K subunit of both mCANP and mu CANP. These antibodies recognized rat mCANP but not chicken CANP, with the exception of one antibody. Examination of the effects of these antibodies on the enzyme activity of mCANP showed that six antibodies partially inhibited the enzyme activity and the others were noninhibitory. These monoclonal antibodies should be useful for analyzing the fine structure of CANPs and the mechanism of the activation of mCANP, and also for determining the intracellular localization of mCANP.