Thermolysin \Ther`mo*ly"sin\, n. [Thermo- + Gr. ly`ein to loose + -in.] (Biochem.) a proteolytic enzyme obtained from the bacterium {Bacillus thermoproteolyticus}, which hydrolyses the N-terminal amide bonds of hydrophobic amino acid residues in proteins. It is used in studies of protein structure. It has a molecular weight of about 37,500 and contains zinc and calcium in its active configuration. --[MI11] [PJC]