Intestine enzymes

MiTJANS M, GARCIA L, MARRERO E, viNARDELL M p (2001) Study of Ligmed-A, anantidiarrheal drug based on lignin, on rat small intestine enzyme activity and morphometry. J Vet Pharmacol Then 24 349-51. 

Myo-inositol is one of the most biologically active forms of inositol. It exists in several isomeric forms, the most common being the constituent of phospholipids in biological cell membranes. It also occurs as free inositol and as inositol hexaphosphate (IP6) also known as phytate which is a major source from food. Rice bran is one of the richest sources of IP6 as well as free inositol. Inositol is considered to belong to the B-complex vitamins. It is released in the gastrointestinal tract of humans and animals by the dephosphorylation of IP6 (phytate) by the intestinal enzyme phytase. Phytase also releases intermediate products as inositol triphosphate and inositol pentaphosphate. Inositol triphosphate in cellular membrane functions as an important intra- and intercellular messenger, that merits its value as a nutritional therapy for cancer. 

Bicarbonate is only one of the digestive chemicals that get secreted into the small intestines. Bile acids play a role as well. Bile is made in the liver, stored in the gallbladder, and, when needed, secreted into the small intestines via the bile duct. Bile plays an essential role in the breakdown of fat by dissolving it in the small intestine, much like soap dissolves oil on a frying pan. This breaks the fat down into small droplets. These fat droplets are broken down even further by other intestinal enzymes so that they can be absorbed by the body. 

D Fleisher, BH Stewart, GL Amidon. Design of prodrugs for improved GI absorption by intestinal enzyme targeting. Methods Enzymol 112 360-381, 1985. 

G Gwinup, AN Elias, ES Domurat. Insulin and C-peptide levels following oral administration of insulin in intestinal-enzyme protected capsules. Gen Pharmacol 22 143-246, 1991. 

Goodman, D. S. and H. S. Huang. 1965. Biosynthesis of vitamin A with rat intestinal enzymes. Science 149 879-880. 

E. Krondahl, H. von Euler-Chelpin, A. Orzechowski, G. Ekstrom, H. Lennernas, Investigation of the in-vitro Metabolism of Three Opioid Tetrapeptides by Pancreatic and Intestinal Enzymes ,./. Pharm. Pharmacol. 2000, 52, 785 - 795. 

In this chapter we survey recent findings that describe the metabolic fate of the xenobiotic moieties of mercapturic acid pathway (MAP) metabolites that are excreted from the liver with the bile. We show that the products of the MAP undergo an enterohepatic circulation that is mediated by intestinal enzymes and/or intestinal microflora. 

LueBen, H.L., De Leeuw, J., Perard, D., et al. (1996). Mucoadhesive polymers in peroral peptide drug delivery. I. Influence of mucoadhesive excipients on the proteolytic activity of intestinal enzymes. Eur. J. Pharmaceut. Sci., 4, 117-128. 

The mechanism of action of anticholinesterases is to form a stable covalent complex with the Achase enzyme. Achase is one of several enzymes known as serine esterases. Other examples include the intestinal enzymes trypsin and chymotrypsin as well as the blood clotting agent thrombin. During the course of the catalysis the alcohol -OH of a serine side chain in the active site of the enzyme forms an ester complex, called the acyl-enzyme, with the substrate. So, acetylcholine will go through similar chemical reactions with Achase. 

In the living organism, the conjugated diethylstilbestrol reaching the gut with the bile is hydrolyzed by intestinal enzymes and then is available for enterohepatic circulation. Metabolism of diethylstilbestrol is similar among species a major part of the administered dose is eliminated as unchanged diethylstilbestrol, but it is different in respect to the type of the metabolites formed. 

At room temperature alkaline phosphatases are generally stable in neutral or mildly alkaline solution but are sensitive to inactivation by acid. Unfortunately, most stability data refer to impure preparations and some of the following statements may need modifying when further information is available. Scutt and Moss investigated the denaturation of human liver and intestinal enzymes at pH 2.1 and 0° (92). The liver enzyme was significantly more labile, and both enzymes could be par-... 

In chapter 8, we mentioned that the pancreas secretes trypsin, chymotrypsin, and elastase as inactive zymogens, which are activated by extracellular proteases. Trypsin is activated when the intestinal enzyme enter-opeptidase cuts off an N-terminal hexapeptide. Trypsin in turn activates chymotrypsin by cutting it at the N-terminal end between Arg 15 and lie 16. This type of change in the covalent structure of an enzyme is termed partial proteoly-sis. Delaying the activation prevents the digestive enzymes from destroying the pancreatic cells in which they are synthesized. 

Fleisher, D., et al. 1986. Oral absorption of 21-corticosteroid esters A function of aqueous stability and intestinal enzyme activity and distribution. J Pharm Sci 75 934. 

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