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GI Physiology > Digestive Enzymes > Flashcards

Digestive Enzymes Flashcards

1
Q

Carbohydrate Digestive Enzymes:
Mouth (2 in oral cavity)
Small Intestine (1 in lumen, 6 on brush border)

A

Mouth: salivary alpha-amylase and lysozyme
Small Intestine: pancreatic alpha-amylase (lumen) and glucoamylase, dexrinase, sucrase-isomaltase, maltase, lactase-cerebrosidase, trehalase (brush border)

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2
Q

Salivary alpha-Amylase:
Area of Operation
Specific Cleavage Function (Factors and Products)
Limitations

A

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

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3
Q

Lysozyme:
Area of Operation
Specific Cleavage Function (Factors and Products)
Main Physiological Function

A

Mouth
Cleaves beta(1-4) glycosidic bonds in peptidoglycans
Kill bacteria in mouth

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4
Q

Pancreatic alpha-Amylase:
Areas of Production and Operation
Specific Cleavage Function
Factors and Products

A 
Produced in pancreas and secreted into small intestine
Cleaves alpha(1-4) glycosidic bonds of starch to glucose, maltose, maltotriose and alpha-limit dextran
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5
Q

Glucoamylase:
Area of Operation
Specific Cleavage Function
Factors and/or Products

A

Small intestine brush border
Exoglycosidase of alpha(1-4) bonds at nonreducing end of starches
Products - maltose and maltotriose

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6
Q

Dextrinase:
Area of Operation
Specific Cleavage Function
Factors and/or Products

A 
Small intestine brush border
Cleaves dextrins (low molecular weight oligosaccharides) produced by earlier hydrolysis
Factor - alpha-limit dextran
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7
Q

Sucrase-Isomaltase:
Area of Operation
Specific Cleavage Function
Factors and/or Products

A

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

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8
Q

Maltase:
Area of Operation
Factors and Products

A

Small intestine brush border

Cleaves maltose into 2 glucose molecules

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9
Q

Lactase-Cerebrosidase:
Area of Operation
Factors and/or Products

A

Small intestine brush border
Lactase: cleaves lactose into glucose and galactose, and cellobiose into 2 glucose molecules
Cerebrosidase: cleaves glucocerebroside and galactocerebroside (glycosphingolipids)

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10
Q

Trehalase:
Area of Operation
Factors and/or Products
Where it is Found

A

Small intestine brush border
Cleaves trehalose into 2 glucose molecules
Common in mushrooms and insects

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11
Q

Protein Digestive Factors and Enzymes:
Stomach (1 factor, 1 enzyme)
Small Intestine (7)

A

Stomach: gastric acid, pepsin

Small intestine: trypsin, chymotrypsin, elastase, carboxypeptidases A and B, aminopeptidases, dipeptidases

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12
Q

Significance of gastric acid for proteins.

A

Facilitates denaturing of dietary protein

Makes peptide bonds more accessible for proteases

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13
Q 
Pepsin:
Production and Activation
Area of Operation
Specific Cleavage Function
Factors and/or Products
Inactivation
A

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

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14
Q 
Trypsin:
Production and Activation
Area of Operation
Specific Cleavage Function
Factors and/or Products
A

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

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15
Q 
Chymotrypsin:
Production and Activation
Area of Operation
Specific Cleavage Function
Factors and/or Products
A

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

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16
Q 
Elastase:
Production and Activation
Area of Operation
Specific Cleavage Function
Factors and/or Products
A

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

17
Q 
Carboxypeptidases A and B:
Production and Activation
Area of Operation
Specific Cleavage Function
Factors and/or Products
A 
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
18
Q

Aminopeptidase:
Area of Operation
Specific Cleavage Function

A

Small intestine brush border

Exopeptidase - cleaves off one AA from N-terminus

19
Q

Dipeptidase:
Area of Operation
Specific Cleavage Function

A

Small intestine brush border

Cleaves dipeptides into AAs

20
Q

Lipid Digestive Enzymes:
Preparation (1 mouth, 1 stomach)
Small Intestine (1 factor, 2 enzymes)
Define “Emulsification”

A

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)

21
Q

Bile Salts:
Production, Storage and Secretion
Purpose (2)

A

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)

22
Q

Lingual Lipase:
Specific Cleavage
Products

A

Cleaves small percentage of dietary fat

Produces monoglycerides, diglycerides and free fatty acids

23
Q

Gastric Lipase:
Description
Specific Cleavage
Products

A

Acid-tolerant emulsification enzyme that digests 10 to 20% of dietary fat
Cleaves triglycerides
Produces monoglycerides, diglycerides and free fatty acids

24
Q

Pancreatic Lipase:
Production and Secretion
Specific Cleavage
Products

A

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

25
Q

Colipase:
Production, Secretion and Activation
Purpose

A

Produced by pancreas as procolipase and secreted into small intestine to be activated by trypsin
Maintains activity of pancreatic lipase in presence of bile salts

26
Q

Nucleic Acid Digestive Enzymes:
Small Intestine Lumen (4)
Small Intestine Brush Border (2)

A

Lumen: DNAases, RNAases, exonucleases, endonucleases

Bursh border: nucleosidases and phosphatases

27
Q 
DNAases, RNAases, Exonucleases and Endonucleases:
Function
DNAase Products (given DNA strand)
RNAase Products (given RNA strand)
A

Break down nucleic acids into monomeric nucleotides
DNAase: dATP, dGTP, TTP, dCTP (notice TTP)
RNAase: ATP, GTP, UTP, CTP

28
Q

Nucleosidases:
Specific Cleavage
Products

A

Cleave ribose or deoxyribose and nitrogenous bases

Adenine, guanine, cytosine, thymine, uracine)

29
Q

Phosphatases:
Specific Cleavage
Products

A

Cleave phosphate groups and nucleotides

Adenosine, deoxyadenosine, cytidine, deoxycytidine, thymidine, guanosine, deoxyguanosine, uridine

30
Q

Microbial-Based Digestion in Humans:
Define “Dietary Fiber” and Give Examples (6)
Products of Bacterial Digestion (7)

A

Dietary fiber - plant polymers resistant to human digestive enzymes that help move food along GI tract by providing bulk (ex. cellulose, hemicellulose, inulin, pectin, lignin, suberin)
Products - hydrogen gas, methane, carbon dioxide, acetate, propionate, butyrate, lactate

GI Physiology (4 decks)

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