leky-latky/enzymy/lipasy
Štěpení tuků
Lingual lipase
- Secreted by a serous gland
- Back of the tongue
- Initiates fat digestion
17 HGL
- Chief cells of the fundic mucosa of the stomach
- Broad pH range (3 to 6)
- Stable even at the low pH present in the stomach
Pancreatic lipolytic enzymes
- Acinar cells of the pancreas
- Colipase-dependent lipase
- Classical pancreatic lipase
- Triacylglycerol acyl hydrolase (HPL)
- Pancreatic lipase related-protein 1 and 2 (HPLRP1, HPLRP2)
- Carboxyl ester hydrolase
- Bile salt stimulated lipase
- Carboxyl ester lipase
- cholesterol esterase
- cholesterol ester lipase
- Human milk lipase
- Monoglyceride lipase
- Pancreatic non-specific lipase
- Phospholipase A2 [12]
- Cholesterol esters, lipidic vitamin esters, monoglycerides, diglycerides, TG, and phospholipids
- Hydrolyzed mainly by carboxyl ester hydrolase [12]
Colipase
- A factor that is necessary to optimize pancreatic lipase activity
- Binds to
- Bile acid micelles
- Phospholipid-covered emulsions
- Facilitates the interaction between pancreatic lipase and the surface of emulsified lipid droplets [12]
HPLRP1 and -2
- HPLRP1
- Does not exert lipolytic activity [12]
- HPLRP2 hydrolyzes
- Galactolipids
- Phospholipids
- TG at a low rate
- Retinyl ester
- Does not need colipase to be active [12]
Gastric 17 HGL
- Hydrolysis of dietary TG
- Starts in the stomach
- Catalytic action of HGL
- Secretion of HGL is induced by
- Mechanical stimulation of the stomach
- Ingestion of food
- Sympathetic activation
- Hydrolyzes 5% to 40% of ingested TG
- Mainly generating FFA, diglycerides
- Few 2-MG molecules
- Crucial for the continuation of the digestion process in the duodenum by HPL
- Gastric lipolysis ensures:
- Lipid emulsification
- Lipid–water interface
- Generation of long-chain FFA
- In the duodenum, will stimulate the release of
- Cholecystokinin (CCK)
- HPL secretion
- Slowing down gastric emptying [12]
- Generation of diglycerides
- Hydrolyzed more effectively than TG
- Hydrolysis of TG persists in the duodenum
- Combined actions of HGL - further lipolysis contributing 7.5% to total lipolysis in the duodenum
- HPL
- Bile salts [12]
HPL
- Principal pancreatic lipolytic enzyme
- Hydrolyzes 40% to 70% of TG
- Yielding 2-MG and long-chain saturated and polyunsaturated FFA
- Requires the presence of colipase [12]
Colipase
- Secreted as a precursor molecule
- In the presence of bile salts, pro-colipase binds
- Without inducing any conformational change
- To the C-terminal domain of the HPL molecule [12]
Transport
- Bile-derived mixed micelles convert FFA and 2-MG into soluble aggregates
- Micelles transport these lipolytic products from the intestinal lumen to the intestinal walls [12]
- Contact with the enterocyte
- Molecules are transported across the cell membrane [12]
Enterocyte
- Re-esterifies 2-MG and FFA into TG
- Assembles them into chylomicrons
- Secretes these into the lymphatic system [12]
Lipolysis rates and consequently FFA supply
- Can be affected by several factors
- Lipase levels
- Lipase activity
- Physicochemical properties of dietary lipids
- Presence of inhibitors or enhancers [12]
