The effect of aqueous methanol on the catalytic properties of porcine pancreatic lipase has been investigated. The kcat values for the hydrolysis of Nα-benzyloxycarbonyl-L-lysine p-nitrophenyl ester at 0°C increased in a linear manner with increasing methanol concentration. However, the KM values were not influenced at methanol concentrations lower than 30% and then began to increase at higher concentrations in an exponential fashion. Based on product analysis, the increase in kcat with increasing methanol concentration can be accounted for by nucleophilic competition of methanol for the acyl enzyme intermediate, indicating that the rate-limiting step of the porcine pancreatic lipase-catalyzed reaction is deacylation under current experimental conditions. The exponential increase in KM at methanol concentrations higher than 30% is attributed to the hydrophobic partitioning effect on substrate binding. There was no loss of lipase activity over a 4 h period in 60% methanol concentration at pH* 5.5 and 0°C. By monitoring the intrinsic fluorescence and absorbance, no evidence for structural changes by methanol was observed.
|Number of pages
|Journal of microbiology and biotechnology
|Published - 2005 Apr
- Methanol solvent
- Rate-limiting step
ASJC Scopus subject areas
- Applied Microbiology and Biotechnology