THERMOSTABILITY OF HIGH-ACTIVITY ALKALINE PROTEASE FROM CONIDIOBOLUS-CORONATUS (NCL-86.8.20)

Conidiobolus coronatus (NCL 86.8.20) produces high levels of protease activity (30 U ml(-1)). The ease of microbe-free enzyme preparation an d its compatibility with most of the commercial detergents are the adv antageous features of Conidiobolus protease. The enzyme was stable at 28 degrees C for 20 h and at 40 degrees C for 1 h, but was completely inactive on incubation at 50 degrees C for I h. Higher thermostability is an important factor for the suitability of its application in dete rgents. The effect of a wide variety of compounds was studied to enhan ce the thermal stability of the protease by modification of its microe nvironment. Urea (2-4 M), sodium dodecyl sulfate (1%), NaCl (200 mM), and beta-mercaptoethanol (10 mM) did nor improve the stability of the enzyme. Ethylene glycol (10%), glycerol (1%), sorbitol (800 mM), and P EG-8000 (200 mM) had a marginal effect in preventing the thermal inact ivation of the protease. Casein (0.5%) was also unable to increase the stability of the enzyme at 50 degrees C. Addition of Ca2+ (25 mM) or glycine (1 M) was effective in increasing the half-life of the enzyme three-fold. The enzyme retained 43% of its activity at 50 degrees C in the presence of Ca2+ and glycine. The enzyme showed compatibility at 50 degrees C with commercial detergents such as Revel and Ariel in pre sence of Ca2+.