Lipase Enzyme

Lipase enzymes are fat hydrolysing enzymes. They are secreted from various organs, e.g. pancreas, intestine, gastric juice, adipose tissues, lysosomes, blood, etc. They hydrolyse triglycerides and other dietary fats to fatty acid and glycerol. They are a subclass of esterase enzymes, splitting ester to acid and alcohol.

In most of the living organisms, they are essential for digestion and transportation of lipids.

Lipase Enzyme Function and Types

Lipases are essential for various biological processes. The main function of lipases is the breakdown and transport of dietary lipids. Various types of lipases are involved in diverse processes such as fat metabolism, transportation, cell signalling, inflammation, etc.

Types of Lipase Enzyme Secretion and Function
Lingual lipase Present in saliva and catalyse initial triglyceride digestion.
Gastric lipase Present in gastric juice, here fat digestion is limited to triglycerides with short-chain fatty acids.
Pancreatic Lipase Present in pancreatic secretion, it is the most important lipolytic enzyme. It hydrolyses most of the dietary fats to fatty acids and glycerol. Bile salts accelerate the function of pancreatic lipase.
Lysosomal acid lipase They are present intracellularly in lysosomes. They regulate intracellular lipid stores. They degrade lipoproteins, that come by endocytosis.
Lipoprotein lipase Present on the surface of cells, lining blood capillaries in adipose tissues and muscle. It hydrolyses triglycerides in the blood that is carried by lipoproteins from different organs.

Chylomicrons carry triglycerides from the intestine and VLDL lipoproteins carry triglycerides from the liver to bloodstream.

Phospholipase It hydrolyses phospholipids and takes part in the cell signalling pathways.

Phospholipases help in recycling the cell membrane constituents.

There are different classes of phospholipases. Phospholipase A2 is present in pancreatic secretion in an inactive form, which gets activated by the action of trypsin enzyme.

Phospholipase in snake venom breaks down the cell membrane of the victim.

Lecithin cholesterol acyltransferase (LCAT) It is involved in cholesterol transport.

How does Lipase work?

Digestion and absorption of Fat

Digestion of fat begins in the mouth by the action of lingual lipase present in the saliva. Most of the fat present in the diet is digested in the duodenum by the action of pancreatic lipase. Lipase enzyme is water-soluble, so it can act only on the surface of fat molecules. Emulsification by bile salt breaks down the bigger fat molecules to smaller droplets and greatly enhances the surface area of fat molecules to be acted on by pancreatic lipase. Triglycerides are then hydrolysed to diglycerides, monoglycerides, fatty acid and glycerol.

The resultant fatty acids and glycerol are taken up by the intestinal wall. Triglycerides are re-synthesised there and get transported to adipose, muscle and other tissues. Lipase present in the bloodstream again acts on these triglycerides and the resultant fatty acids and glycerol are taken up by tissues.

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