Digestive Enzymes Flashcards
Carbohydrate Digestive Enzymes:
Mouth (2 in oral cavity)
Small Intestine (1 in lumen, 6 on brush border)
Mouth: salivary alpha-amylase and lysozyme
Small Intestine: pancreatic alpha-amylase (lumen) and glucoamylase, dexrinase, sucrase-isomaltase, maltase, lactase-cerebrosidase, trehalase (brush border)
Salivary alpha-Amylase:
Area of Operation
Specific Cleavage Function (Factors and Products)
Limitations
Mouth
Cleaves alpha(1-4) glycosidic bonds of starch to glucose, maltose, maltotriose and alpha-limit dextran
Limited by pH - operates in saliva, digested in stomach
Lysozyme:
Area of Operation
Specific Cleavage Function (Factors and Products)
Main Physiological Function
Mouth
Cleaves beta(1-4) glycosidic bonds in peptidoglycans
Kill bacteria in mouth
Pancreatic alpha-Amylase:
Areas of Production and Operation
Specific Cleavage Function
Factors and Products
Produced in pancreas and secreted into small intestine Cleaves alpha(1-4) glycosidic bonds of starch to glucose, maltose, maltotriose and alpha-limit dextran
Glucoamylase:
Area of Operation
Specific Cleavage Function
Factors and/or Products
Small intestine brush border
Exoglycosidase of alpha(1-4) bonds at nonreducing end of starches
Products - maltose and maltotriose
Dextrinase:
Area of Operation
Specific Cleavage Function
Factors and/or Products
Small intestine brush border Cleaves dextrins (low molecular weight oligosaccharides) produced by earlier hydrolysis Factor - alpha-limit dextran
Sucrase-Isomaltase:
Area of Operation
Specific Cleavage Function
Factors and/or Products
Small intestine brush border
Sucrase: cleaves sucrose into fructose and glucose, maltose into 2 glucose molecules, and maltotriose into 3 glucose molecules
Isomaltase: cleaves alpha(1-6) bonds in isomaltose and alpha-limit dextran
Maltase:
Area of Operation
Factors and Products
Small intestine brush border
Cleaves maltose into 2 glucose molecules
Lactase-Cerebrosidase:
Area of Operation
Factors and/or Products
Small intestine brush border
Lactase: cleaves lactose into glucose and galactose, and cellobiose into 2 glucose molecules
Cerebrosidase: cleaves glucocerebroside and galactocerebroside (glycosphingolipids)
Trehalase:
Area of Operation
Factors and/or Products
Where it is Found
Small intestine brush border
Cleaves trehalose into 2 glucose molecules
Common in mushrooms and insects
Protein Digestive Factors and Enzymes:
Stomach (1 factor, 1 enzyme)
Small Intestine (7)
Stomach: gastric acid, pepsin
Small intestine: trypsin, chymotrypsin, elastase, carboxypeptidases A and B, aminopeptidases, dipeptidases
Significance of gastric acid for proteins.
Facilitates denaturing of dietary protein
Makes peptide bonds more accessible for proteases
Pepsin: Production and Activation Area of Operation Specific Cleavage Function Factors and/or Products Inactivation
Produced and secreted as pepsinogen by gastric chief cells and stimulated by gastric acid for autocleavage from N-terminus
Stomach (operational at pH 1.5 - 2.0)
Endopeptidase - cleaves nonterminal and terminal peptide bonds on amino side of hydrophobic AAs
Carboxyl protease - Asp protease (catalyzed by Asp)
Produces peptone (mixture of oligopeptides and free AAs)
Inactivated by high pH in duodenum
Trypsin: Production and Activation Area of Operation Specific Cleavage Function Factors and/or Products
Produced and secreted as trypsinogen by pancreas and activated by trypsin or enteropeptidase
Endopeptidase - cleaves peptide bonds on carboxyl side of Lys and Arg except when followed by Pro
Ser protease
Chymotrypsin: Production and Activation Area of Operation Specific Cleavage Function Factors and/or Products
Produced and secreted as chymotrypsinogen by pancreas and activated in intestinal lumen by trypsin (active forms - pi-chymotrypsin and alpha-chymotrypsin)
Endopeptidase - cleace peptide bonds on carboxyl side of hydrophobic AAs
Elastase: Production and Activation Area of Operation Specific Cleavage Function Factors and/or Products
Produce and secreted as proelastase by pancreas and activated in intestinal lumen by trypsin
Endopeptidase - cleaves peptide bonds on carboxyl side of small amino acids (ex. Gly)
Ser protease
Carboxypeptidases A and B: Production and Activation Area of Operation Specific Cleavage Function Factors and/or Products
Produce and secreted as procarboxypeptidases by pancreas and activated in intestinal lumen by trypsin Exopeptidases A: cleaves of hydrophobic AAs B: cleaves off basic AAs Zn2+ metalloprotease
Aminopeptidase:
Area of Operation
Specific Cleavage Function
Small intestine brush border
Exopeptidase - cleaves off one AA from N-terminus
Dipeptidase:
Area of Operation
Specific Cleavage Function
Small intestine brush border
Cleaves dipeptides into AAs
Lipid Digestive Enzymes:
Preparation (1 mouth, 1 stomach)
Small Intestine (1 factor, 2 enzymes)
Define “Emulsification”
Mouth: lingual lipase
Stomach: gastric lipase
Small intestine: bile salts (factor), pancreatic lipase, colipase
Emulsification - creation of a mixture of a two-phase solution (ex. fat and water)
Bile Salts:
Production, Storage and Secretion
Purpose (2)
Produced and secreted in bile by hepatocytes
Stored in gallbladder
Secreted into small intestine
Leads to greater emulsification (mixed micelle formation)
Necessary for absorption of other dietary lipids (ex. cholesterol and fat-soluble vitamins)
Lingual Lipase:
Specific Cleavage
Products
Cleaves small percentage of dietary fat
Produces monoglycerides, diglycerides and free fatty acids
Gastric Lipase:
Description
Specific Cleavage
Products
Acid-tolerant emulsification enzyme that digests 10 to 20% of dietary fat
Cleaves triglycerides
Produces monoglycerides, diglycerides and free fatty acids
Pancreatic Lipase:
Production and Secretion
Specific Cleavage
Products
Produced by pancreas and secreted into small intestine
Binds to fat emulsion droplets and cleaves triglycerides
Produces 2 free fatty acid anions and a 2-monoacylglycerol molecule
