Thermostability of porcine pancreas lipase in non-aqueous media

Thermostability of Porcine pancreas lipase (PPL) was studied by monitoring esterification activity and A(290) values by ultra-violet (UV) spectroscopy, in the temperature range 40-80 degreesC for incubation periods up to 10 days through Response Surface Analysis. This novel approach to the problem generated information on the behaviour of PPL under different temperatures for longer periods of incubations, which is essential for employment of lipase in esterification reactions which are time consuming and requires higher temperatures and non-polar solvents. Native PPL, PPL in buffer saturated methylisobutyl ketone (MIBK) and PPL in 0.2 M lactic acid in MIBK were subjected to response surface methodological analyses. Native enzyme showed loss of activity at 60 degreesC probably due to a conformation with a greater unfolding at 60 degreesC than at 40 and 80 degreesC. Longer periods of incubation of PPL at especially 80 degreesC did not affect the active conformation of PPL even after incubation for a period upto 10 days. However, the presence of small amounts of buffer stabilizes the enzyme at 60 degreesC contrary to what was observed with the native enzyme. In the presence of 0.2 M lactic acid, there was a general loss in active conformation and hence activity at all temperatures and periods studied. The results from activity measurements were supported by UV spectroscopic data of the same in every respect indicating that variation in conformational changes is responsible for loss in activity. (C) 2001 Elsevier Science Ltd. All rights reserved.