Structural and evolutionary relationships in lipase mechanism and activation

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• Lipases catalyze triglyceride hydrolysis, yielding monoglycerides and glycerol.
• Enzyme activity is significantly enhanced at oil/water interfaces (interfacial activation).
• Understanding the structural basis of interfacial activation is crucial for lipase function.

Purpose of the Study:

• To elucidate the structural and chemical basis of interfacial activation in lipases.
• To compare the structural features of a fungal lipase and a human pancreatic lipase.
• To reveal the evolutionary and mechanistic insights into lipase activity.

Main Methods:

• X-ray crystallography of fungal and human pancreatic lipases.
• Analysis of enzyme-bound substrate analogue complex structures.
• Comparison of catalytic triad, active site accessibility, and overall architecture.

Main Results:

• Both lipases share an Asp:His:Ser catalytic triad, similar to serine proteases, but with different amino acid conformations.
• Catalytic sites are buried by a helical 'lid' structure, inaccessible to solvent.
• Despite divergent evolution and sequence dissimilarity, both enzymes exhibit a similar beta-sheet framework and active site decoration.
• Complex structure shows lid displacement, exposing the active site and altering surface properties.

Conclusions:

• Interfacial activation in lipases is mediated by a mobile 'lid' mechanism.
• The conserved structural framework and active site organization are key to lipase function.
• Structural insights provide a basis for understanding lipase specificity and engineering applications.