Vol. 1, #17
November 26, 2004

Q: What are digestive enzymes and what are they good for? - Layperson

A: Enzymes are essential to the body's absorption and full use of food. The capacity of the living organism to make enzymes diminishes with age, and some scientists believe that humans could live longer and be healthier by guarding against the loss of our precious enzymes.

Enzymes are responsible for every activity of life. Even thinking requires enzyme activity. There are two primary classes of enzymes responsible for maintaining life functions: digestive and metabolic. The primary digestive enzymes are proteases (to digest proteins), amylases (to digest carbohydrates), and lipases (to digest fats). These enzymes function as a biological catalyst to help break down food. Raw foods also provide enzymes that naturally break down food for proper absorption. Metabolic enzymes are responsible for the structuring, repairing, and remodeling of every cell, and the body is under a great daily burden to supply sufficient enzymes for optimal health. Metabolic enzymes operate in every cell, every organ, and every tissue, and they need constant replenishment.

Digestion of food takes a high priority and has a high demand for enzymes. When we eat, enzymatic activity begins in the mouth, where salivary amylase, lingual lipase, and ptyalin initiate starch and fat digestion. In the stomach, hydrochloric acid activates pepsinogen to pepsin, which breaks down protein, and gastric lipase begins the hydrolysis of fats. Without proper enzyme production, the body has a difficult time digesting food, often resulting in almost every variety of chronic disorders-allergies, blood clotting disorders, cancer, degenerative diseases, digestive disorders, electrolyte, hormonal, and mineral imbalances, heart disease, malabsorbtion disorders, metabolic disorders, strokes, and numerous others. The proper amount of enzymes will either correct or prevent these disturbances. The following is a list of enzymes involved in the digestive process:

Digestive Enzymes (in order of exposure to ingested food)

ORAL CAVITY
Ptyalin (salivary amylase) source: parotid, submandibular, and sublingual glands release into oral pharynx, inactivated in low pH action: breaks alpha 1,4 glycosidic bonds in starch to form maltose, maltotriose, and alpha-limit dextrins
Lingual lipase source: lingual gland?, not inactivated at low pH action: breaks TGs to FFAs which stimulate pancreatic lipase (necessary for fat digestion)
Lysozyme source: parotid, submandibular, and sublingual glands action: hydrolyzes B-1,4-glucosidic linkages b/n N-acetylmuramic acid and N-acetylglucosamine in the mucoid cell wall of G- bacteria (breaks peptidoclycan bonds) Lactoferrin binds free Fe to prevent bacterial Fe uptake and growth

ESOPHAGUS
Pepsinogen source: serous cells found in mucous glands within the submucosa action: coverts to pepsin (an endopeptidase) in pH<5 (stomach), cleaves C-terminal of F,L, and E (not V, A, or G) Lysozyme (see above)
STOMACH
Pepsinogen source: secreted by chief cells found in the base of gastric pits, in all parts of the stomach - mainly the body BUT not the cardiac region action: (see above)
Rennin source: chief cells action: cleaves and inactivates kappa-casein to para-kappa-casein and macropeptide (curds milk protein to facilitate its digestion)
Gastric lipase source: chief cells action: hydrolyzes emulsified TGs to 3 FFAs and glycerol HCl (not an enzyme, fucntion: antibacterial, pepsin activation, and digestion) source: parietal (oxyntic) cells, in neck of gastric pit and all parts of the stomach (mainly in the body) secretion mechanism: CO2 + H2O « H2CO3 « HCO3- + H+ antiport in basolateral membrane of bicarbonate, down its gradient, out of cell with chloride transport in, against its gradient Cl- is passed into canaliculi by a chloride channel, which opens into the lumen H+ is pumped out of the cell by H/K ATPase (secondary active transport established by Na/K ATPase on basolateral membrane pumping K in and Na out)
Mucin (not an enzyme, but a protective protein) source: surface-lining cells (isthmus) and mucus neck cells (neck of gastric gland) description: peptide core (lots of S and T, 50% of mucus) saturated with O-linked oligosaccharides (50%), mucins are cross linked by H-bonds formed with water molecules and disulfide covalent bonds
Lysozyme source: MNCs in pylorus action: (see above)

PANCREAS
Pancreatic alpha-amylase source: acinar cells, pH optimum is alkaline, secreted in active form action: (see above)
Pancreatic Lipase source: acinar cells, pH optimum is alkaline, secreted in active form, enhanced activity with bile salts and colipase action: cleaves TG to 2 FFAs and 2-mono-glyceride
Phospholipase A2 source: acinar cells, pH optimum is alkaline, secreted in inactive form action: cleaves lecithin (phosphatidylcholine) to lysolecithin and FFA Secondary alcohol esterase (nonspecific esterase or cholesterol esterase) source: acinar cells, pH optimum is alkaline, secreted in inactive form? action: cleaves secondary alcohol ester to secondary alcohol and FFA
Trypsin source: acinar cells, pH optimum is alkaline, secreted in inactive form (trypsinogen) action: endopeptidase that is activated in the duodenum by enteropeptidase (enterokinase - see below), activates other pancreatic zymogens, cleaves R-X and K-X bonds (not if X=P), cleaves IF from B12 to allow B12 absorption
Chymotrypsin source: acinar cells, pH optimum is alkaline, secreted in inactive form (chymotrypsinogen) action: endopeptidase that cleaves C-terminal of F, Y, and L
Elastase source: acinar cells, pH optimum is alkaline, secreted in inactive form action: endopeptidase that cleaves C-terminal of G, A, S, V, L, and I
Collagenase source: acinar cells, pH optimum is alkaline, secreted in inactive form (procollagenase) action: breaks down collagen into two smaller fragments that can be easily degraded by other proteases
Carboxypeptidases A and B source: acinar cells, pH optimum is alkaline, secreted in inactive form (procarboxypeptidase) action: removes AA at carboxy end of peptide (B cleaves only if the AA is basic - K,L, and ornithine)
Ribonuclease (RNase) source: acinar cells, pH optimum is alkaline action: cleaves the phosphodiester bond between the 5'-ribose of a nucleotide and the phosphate group attached to the 3'-ribose of an adjacent pyrimidine nucleotide
Deoxyribonuclease (DNase) source: acinar cells, pH optimum is alkaline action: cleaves phosphodiester linkages, preferentially adjacent to a pyrimidine nucleotide yielding 5'-phosphate terminated polynucleotides with a free hydroxyl group on position 3'

LIVER
Alkaline phosphatase source: hepatocytes (?), secreted into bile action: hydrolyses phosphate bonds, releasing inorganic phosphate Bile salts (not enzymes, but important in the solubilization of TGs in the intestinal lumen) source: hepatocytes, secreted in bile, concentrated in the gallbladder synthesis: primary bile acid formation: cholesterol is hydroxylated by cholesterol 7-alpha hydroxylase to either cholate (2 OH) or chenodeoxycholate (1 OH) bile salt formation: primary BA is conjugated with glycine (glyco-) or taurine (tauro-) secondary bile acid formation: bacterial enzymes in the gut dehydroxylate and deconjugate the bile salts to form deoxycholate from cholate and lithocholate from chenodeoxycholate secondary bile acid absorption: passive throughout but mainly by active transport in ileum - action: forms micelles with lecithin and cholesterol, emulsifys TGs and increases their availability to lipases

SMALL INTESTINE (NOTE: absorption rules: carbohydrates have to be single units; proteins can be di/tripeptides or single AAs; lipids, cholesterol, and lipophilic vitamins must be unesterified)

Mucins (see above for action and description) Source: Brunner’s glands, goblet cells
Enteropeptidase (enterokinase) Source: Brunner’s glands located in the submucosa of the duodenum, crypts of Lieberkuhn Action: converts trypsinogen to trysin via cleavage of a K-I bond
Lysozyme Source: paneth cells in epithelium Action: (see above)
4 to 5 maltases source: brushborder of enterocytes
action: cleavage of maltose and maltotriose to glucose
Isomaltase Source: brushborder of enterocytes
Action: cleavage of alpha-limit dextrins to glucose Sucrase source: brushborder of enterocytes
action: cleavage of sucrose to fructose and glucose
Lactase Source: brushborder of enterocytes
Action: cleave of lactose to galactose and glucose
Trehalase Source: brushborder of enterocytes
Action: cleavage of alpha 1,1 diglucose to glucose
Brushborder exopeptidase Source: brushborder of enterocytes
Action: hydrolyzes oligopeptides to AAs and di/tripeptides (no brushborder lipases)

COLON - no digestive enzymes are secreted here
Most enzymes taken orally, including those made from pig pancreas extracts, are inactivated by the low pH of stomach acid. Fungal enzymes, however, are acid-resistant, having activity at pH as low as 2.0 and as high as 10. Fungal plants use their enzymes to break down and digest plant material that they grow upon. Since the site of fungal growth in nature can vary, the fungus has evolved enzyme systems that allow the plant to grow under a variety of conditions, including differences in pH. Pancreatic enzymes are designed to work under a much narrower range of pH, since its environment is more controlled. Pancreatic enzymes available as prescription drugs must be enterically coated to provide resistance to acidity. Some of the coatings contain methyl acrylate, which some speculate as the causative agent in fibrosing of the colon seen with prolonged high dosing of pancreatic enzymes.

Drug Interactions

Certain medicines interact with digestive enzymes: Some interactions may increase the need for digestive enzymes, other interactions may be negative and indicate digestive enzymes should not be taken without first speaking with your physician or pharmacist, others may require further explanation Refer to the individual drug article for specific details about an interaction.


November 20, 2004 Newsletter

DISCLAIMER:  The information in this column, is NOT intended to diagnose and/or treat any health related issues and is provided solely for informational purposes only. Consult the appropriate healthcare professional before making any changes to your healthcare regime. Even what may seem like simple changes in the diet for example, can interact with, and alter, the efficiency of medications and/or the body's response to the medications. Many herbs and supplements exert powerful medicinal effects. Neither the author, nor the website designers, assume any responsibility for the reader's use or misuse of this information.

© 2002 Nature's Corner