Proteolytic enzymes of thermophilic bacteria—Part II

Summary

• 1. The thermophilic bacteriaBacillus thermophilus, B. aerothermophilus andB. thermoacidurans produce very active proteinases which appear to be endocellular in character and are found in culture filtrates only as a result of autolysis of the cells.

• 2. Filtrates obtained from broth cultures containing calcium and magnesium salts are proteolytically more powerful than those obtained from cultures prepared with ordinary broth, but the effect of these metals is on the activity of the proteinases and not on the quantity of the enzyme produced.

• 3. Unlike papainases the proteinases of the thermophilic bacteria are not affected by copper ions.

• 4. Activity of the proteinases of thermophilic bacteria is suppressed by methylene blue and is prevented by iodine.

• 5. Although peptone itself is not hydrolysed by the proteinases of thermophilic bacteria, yet it hinders the hydrolysis of gelatin. The evidence obtained tends to show that the effect of peptone is probably due to competition by peptone with the gelatin for attachment to the active centre of the enzyme molecule, or a centre very close to the active centre.