Digestive enzyme excretion

Digestive enzyme excretion Changes to the microbiota in the gut may result in an alteration in intestinal food digestion patterns. Probiotics may provide their host with digestive enzymes and assist in assimilating... 

Metabolism - Acarbose is metabolized exclusively within the Gl tract, principally by intestinal bacteria, but also by digestive enzymes. A fraction of these metabolites (about 34% of the dose) was absorbed and subsequently excreted in the urine. 

There are also a number of enzymes that degrade organic N compounds, inside or outside the cell, thereby making N available for assimilation or uptake, respectively. Examples we will consider include urease, amino acid oxidases, and extracellular peptidases (MulhoUand et al., 2002 MulhoUand and Lee, in revision. Chapter 7 by MulhoUand and Lomas, Fig. 2, this volume Table 32.1). In addition, for heterotro-phic organisms, digestive enzymes, especially proteases, are important for internal N cycling, recouping cellular N, and excretion. 

The normal range of serum zinc in the adult is 11 to IS pM- Urinary zinc is 3(1(1 to 700 pg/day, which is equivalent to 2 to of zinc intake. Most of the absorbed zinc is excreted in the bile and is eventually lost In the feces. Fecal zinc originates from nonabsorbed zinc and from pancreatic secretions and exfoliated enterocyles-The zinc released by the pancreas can be reabsorbed and thus participates in enteropancreatic circulation. Nearly all of the zinc in pancreatic juices is bound to carboxypeptidase A and b. About 1 mg of fecal zinc per day is derived from pancreatic secretions. In any accounting of the nutrients absorbed each day, one needs to realize that the enzymes and salts released in the digestive juices each day (during a meal) actually represent a second meal. The digestive enzymes, for... 

C. The pancreas produces bicarbonate (which neutralizes stomach acid) and digestive enzymes (including the lipase that degrades dietary lipids). Decreased bicarbonate will lead to a decrease of intestinal pH. Decreased digestion of dietary triacylglycerols will lead to formation of fewer bile salt micelles. Intestinal cells will have less substrate for chylomicron formation, and less fat-soluble vitamins will be absorbed. More dietary fat will be excreted in the feces. 

Second, compounds can be actively transported into bile, a process that takes place in the liver. After concentration, bile flows into the intestine. In the intestine, the drugs and metabolites can be excreted through the stool, reabsorbed into the bloodstream, or further degraded by digestive enzymes. Sometimes, compounds are recycled from the bloodstream into the intestine and back into the bloodstream, a process referred to as enterohepalic... 

Thrombin and factor Xa are prominent players in the blood clotting cascade. They are, therefore, important targets for the development of new anticoagulant/antithrombotic drugs. Trypsin is an enzyme excreted by the pancreas for helping in digestion, and has classically been used as a model enzyme for the whole serine protease family. Thus, in order to minimize side-effects of thrombin/factorXa inhibitors, and to enhance their bioavailability, potential drugs should exhibit selectivity towards thrombin/factorXa with respect to trypsin. 

Cyclamate and saccharin are rapidly excreted in the urine, mainly unchanged. Aspartame, a monomethyl ester of aspartylphenylalanine, is degraded by digestive enzymes into its constituent amino acids. Phenyl-ketonurics should limit their intake of aspartame due to its conversion to phenylalanine in the intestine. 

Dietary exposure to PAH was examined in more detail in a controlled CB beef feeding experiment in which each individual served as his own control. Two individuals exhibited measurable increases in PAH-DNA adduct levels while the two other individuals did not respond. This difference could be due to interindividual differences in constitutive or induced physiological parameters such as absorption, digestion, metabolism, excretion and DNA adduct formation and repair (11). Conney et al (12) demonstrated the induction of phenacetin metabolizing enzymes in human volunteers fed CB beef for four days. Variation in the Inducibllity of PAH metabolizing enzymes in hepatocytes and peripheral blood cells in individuals fed CB beef may explain some of the observed interindividual differences in this study. Other studies (13.14) have demonstrated a 3-10 fold variation in the ability of cultured human lymphocytes or monocytes to form B(a)P-DNA adducts after treatment with B(a)P. 

Mammals, fungi, and higher plants produce a family of proteolytic enzymes known as aspartic proteases. These enzymes are active at acidic (or sometimes neutral) pH, and each possesses two aspartic acid residues at the active site. Aspartic proteases carry out a variety of functions (Table 16.3), including digestion pepsin and ehymosin), lysosomal protein degradation eathepsin D and E), and regulation of blood pressure renin is an aspartic protease involved in the production of an otensin, a hormone that stimulates smooth muscle contraction and reduces excretion of salts and fluid). The aspartic proteases display a variety of substrate specificities, but normally they are most active in the cleavage of peptide bonds between two hydrophobic amino acid residues. The preferred substrates of pepsin, for example, contain aromatic residues on both sides of the peptide bond to be cleaved. 

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