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 d ays through Response Surface Analysis. This novel approach to the problem g enerated information on the behaviour of PPL under different temperatures f or longer periods of incubations, which is essential for employment of lipa se in esterification reactions which are time consuming and requires higher temperatures and non-polar solvents. Native PPL, PPL in buffer saturated m ethylisobutyl ketone (MIBK) and PPL in 0.2 M lactic acid in MIBK were subje cted to response surface methodological analyses. Native enzyme showed loss of activity at 60 degreesC probably due to a conformation with a greater u nfolding at 60 degreesC than at 40 and 80 degreesC. Longer periods of incub ation of PPL at especially 80 degreesC did not affect the active conformati on of PPL even after incubation for a period upto 10 days. However, the pre sence of small amounts of buffer stabilizes the enzyme at 60 degreesC contr ary to what was observed with the native enzyme. In the presence of 0.2 M l actic acid, there was a general loss in active conformation and hence activ ity at all temperatures and periods studied. The results from activity meas urements were supported by UV spectroscopic data of the same in every respe ct indicating that variation in conformational changes is responsible for l oss in activity. (C) 2001 Elsevier Science Ltd. All rights reserved.