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The Biosphere
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Enzymes are named for what they do. For example, the enzyme given off by the stomach, which splits proteins as part of the digestion process, is called gastric proteinase. The “gastric” part of the name refers to the enzyme's origin in the stomach. The “proteinase” denotes that it splits up protein molecules. The common name for this enzyme is pepsin. Similarly, the enzyme produced by the pancreas that breaks down fats (lipids) is called pancreatic lipase. Its common name is steapsin. In general, lipase enzymes cause lipid triglycerides to dissociate and form glycerol and fatty acids.
Enzymatic Reaction Kinetics
Published in Debabrata Das, Debayan Das, Biochemical Engineering, 2019
The pH of the reaction mixture largely affects the enzymatic reaction. It may be noted that there is an optimum pH for each enzyme. For example, stomach has the enzyme pepsin, which has an optimum pH between 2 and 3.3, while the optimum pH of amylase, from saliva, is 6.8. Chymotrypsin, from the pancreas, has an optimum pH in the mildly alkaline region between 7 and 8. Enzymes are protein consisting of amino acid residues. The pH of such solutions may be acidic, basic, or neutral based on the negative or positive charge. For example, glutamic acid is acidic at a lower pH, and the increase in pH ionizes glutamic acid. On the other hand, an amino acid lysine is basic in the range of higher pH value. As the pH is decreased, lysine is ionized. An enzyme is catalytically active when each of the amino acid residues at the active site possesses a particular charge. Therefore, the fraction of the catalytically active enzyme depends on the pH.
Estimating the proportion of bioaccessible lead (BaPb) in household dust wipe samples: a comparison of IVBA and PBET methods
Published in Journal of Environmental Science and Health, Part A, 2023
Chandima Wekumbura, Ganga M. Hettiarachchi, Christina Sobin
Glycine is an important constituent of metabolic activities[58] and is also used as a buffering agent. Glycine at low concentrations prevents pH decrease in solutions.[59] When it is used at a significantly lower pH value it has a higher opportunity to regulate that pH. Therefore, when pH 1.5 is used with glycine buffer IVBA rarely exceeds the initial solution pH ± 0.5 after one hour of extraction time as restricted by the method.[43] Both, pH 1.5 and 2.5 with glycine were buffered the pH within this limit (±0.5) in the current study. Ruby et al.[15] adopted PBET from Miller et al.[60] which was originally developed for evaluating an in vitro method for estimation of iron availability from meals. Pepsin is the major constituent in PBET, the powerful enzyme in gastric juice that digests proteins within the normal gastric juice pH 1.5–2.5 when the presence of HCl. Acidification of the samples to pH 2 or 4 is important because pepsin begins to denature itself and thus will lose its activity at pH ≥ 5.[61] In several animal feeding studies, PBET 2.5 best represented bioaccessible lead concentration as compared to PBET pH 1.5 and 2.0.[44]
Novel assay format for proteins based on magnetic molecularly imprinted polymer nanoparticles—detection of pepsin
Published in Journal of the Chinese Advanced Materials Society, 2018
Elena V. Piletska, Joanna Czulak, Stanislav S. Piletsky, Antonio Guerreiro, Francesco Canfarotta, Sergey A. Piletsky
Pepsin is a protease enzyme present in the gastric juice of the stomach, where it digests proteins. The development of analytical test-systems for the quantification of pepsin is important because of its connection to ulcerogenic protease activity. The concentration of pepsin present in the basal gastric juice is about 12 µg mL−1, which could increase up to 33 µg mL−1 depending on the condition or drug used.[1] Although pepsin is produced only in the stomach, it can also be found in the saliva of gastroesophageal reflux disease (GORD) patients.[2] The possibility of detecting and measuring pepsin in clinical samples could provide an objective assessment of conditions and allow clinicians to make a timely diagnosis. Among the commercial test-systems available for the quantification of pepsin is Peptest, which measures pepsin in saliva and enzyme-linked immunosorbent assay ELISA test kits which allow measurement of pepsin concentration in the gastric juice.[3,4]