Lipases

Lipases are enzymes that catalyze the hydrolysis of triacylglycerols (fats) into glycerol and free fatty acids. They are a diverse group of hydrolases found in many organisms, including animals, plants, and microorganisms. Lipases can be secreted or intracellular and play essential roles in digestion, lipid mobilization, and lipid metabolism.

Most lipases are serine hydrolases characterized by a catalytic triad of serine, histidine, and aspartate (or glutamate) and a conserved motif surrounding the catalytic serine, typically a GXSXG sequence. Many lipases exhibit interfacial activation, where activity increases when lipids are presented at an interface. Some lipases possess a lid domain that covers the active site and opens upon contact with lipid surfaces.

Key classes and locations include pancreatic lipase, gastric lipase, hepatic lipase, and lipoprotein lipase. Pancreatic lipase, with its cofactor colipase, functions in the small intestine to digest dietary fats. Lipoprotein lipase acts on circulating lipoproteins, while hepatic lipase participates in remnant metabolism. In adipose tissue pathways, enzymes such as adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) regulate triglyceride mobilization. Microbial lipases are widely used in industry.

Structure-wise, many lipases adopt a (α/β) hydrolase fold and, in eukaryotes, may feature a lid that regulates access to the active site. Regulation often involves cofactors, surface emulsification, and (for pancreatic lipase) bile salts and colipase to facilitate substrate access.

Clinically, serum lipase levels are used to diagnose pancreatitis; elevated lipase can indicate pancreatic injury. Industrial applications include biodiesel production, food processing, and detergent formulations.