HGL is an acid stable lipase that is secreted by the fundic mucosa of the stomach and that hydrolyses dietary triglycerides. Native HGL (molecular mass 50 kDa) is a highly glycosylated protein, the glycan part amounting to 14% of the total molecular mass of the protein. Several isoforms of native HGL have been described and purified. Partial enzymatic deglycosylation of HGL reduced the apparent molecular mass and resulted in the appearance of a mixture of totally (molecular mass 43 kDa) and partially deglycosylated HGL, without any loss of the lipase activity on tributyrin as substrate. Glycosylation thus does not seem to be essential for lipase activity. Expression of HGL in E coli however, led to the production of an inactive protein. It was possible to obtain an active recombinant protein in the baculovirus/insect cell system, which was nevertheless less glycosylated (estimated molecular mass 45 kDa) than the native one. By directed mutagenesis of each of the four potential glycosylation sites and characterisation of each purified mutants, it was possible to ascertain the role of glycosylation (mainly a protection role against pepsin degradation in the stomach).
Buy this Article