Thermolysin (EC 3.4.24.27, Bacillus thermoproteolyticus neutral proteinase, thermoase, thermoase Y10, TLN) is a thermostable neutral metalloproteinase enzyme produced by the Gram-positive bacteria Bacillus thermoproteolyticus.[2] It requires one zinc ion for enzyme activity and four calcium ions for structural stability.[3] Thermolysin specifically catalyzes the hydrolysis of peptide bonds containing hydrophobic amino acids. However thermolysin is also widely used for peptide bond formation through the reverse reaction of hydrolysis.[4] Thermolysin is the most stable member of a family of metalloproteinases produced by various Bacillus species. These enzymes are also termed 'neutral' proteinases or thermolysin -like proteinases (TLPs).