beta 5 ' Loop of turkey pancreatic lipase: Involvement in the resistance to interfacial denaturation

beta 5' Loop is a hydrophobic loop in the C-terminal domain of pancreatic lipases playing an important role in the interaction with lipid-water interface. The turkey pancreatic lipase (TPL) 5 loop N404, S406, and V408 residues were mutated to Y, N, and I, respectively, to replace TPL 5 loop by those of human pancreatic lipase (HPL), which denatures rapidly in the tributyrin-water interface, in order to investigate the involvement of theses 5 loop residues in the pancreatic lipases interfacial stability. TPL Mut 5 was expressed in Pichia pastoris, the mutated enzyme was purified and interfacial properties study showed that TPL Mut 5 interfacial denaturation was faster than that of wild type TPL, which is resistant to interfacial denaturation unlike many pancreatic lipases such as HPL. TPL Mut 5 activity in the absence of tension-active reagents was clearly lower than that of TPL. This decreased activity was more pronounced at high temperatures. Thus mutations (N404-Y, S406-N, and V408-I) introduced in the TPL 5 loop changed the TPL behavior at tributyrin-water interface to be similar to HPL. These TPL 5 loop residues could be responsible for the TPL interfacial stability at high temperatures and in the absence of bile-salts. Practical applications: In contrast to classical pancreatic lipases, turkey pancreatic lipase has a high stability at the lipid-water interface and this property makes it suitable for detergency applications. Here we have studied the 5 loop residues responsible for the interfacial stability.