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The Structure of Pyruvate Carboxylase
Published in D. B. Keech, J. C. Wallace, Pyruvate Carboxylase, 2018
John C. Wallace, Simon B. Easterbrook-Smith
As noted in Section III.G.1, all four subunits in chicken liver pyruvate carboxylase have an N-acetyl group on the amino-terminal residue(s) and are, therefore, not susceptible to sequence determination by the Edman degradation procedure. However, recent experiments by Khew et al.441 have shown that a brief exposure of the native enzyme to low concentrations of chymotrypsin achieves a rapid but selective cleavage of each subunit. When samples of this partial digest were analyzed by SDS-PAGE it was evident that the 112-kDa polypeptide chain had been almost quantitatively converted to a 75-kDa fragment plus smaller pieces. When this 75-kDa species was isolated and subjected to Edman degradation in the gasphase protein sequencer403 (Applied Biosystems, Inc.), an unambiguous N-terminal sequence of 23 residues could be deduced from an analysis of the PTHamino acid derivatives by reverse-phase HPLC. These results indicate that in all four subunits there are regions of high susceptibility to proteolysis, with cleavage in at least one of these, yielding 75-kDa fragments having identical N-terminal sequences for at least 23 residues.
The accessory organs: Pancreas, liver and gallbladder
Published in Paul Ong, Rachel Skittrall, Gastrointestinal Nursing, 2017
A number of proteases are produced by acini cells in the pancreas. Two important ones are trypsin and chymotrypsin. As with pepsin in the stomach, these enzymes are manufactured in the inactive forms of trypsinogen and chymotrypsinogen to prevent autodigestion of pancreatic tissue. Trypsinogen is converted to the active trypsin by the enzyme enterokinase which is secreted by intestinal enterocyte epithelial cells. Once formed trypsin also has the effect of activating trypsinogen and chymotrypsinogen. Both trypsin and chymotrypsin destroy the peptide bonds linking amino acids together. This serves to break down polypeptides to peptides, therefore making peptide chains shorter, but these proteases cannot break down the peptides to the single molecule amino acids. This role is largely performed by peptidases. This is an enzyme released from the brush border membrane of the intestinal enterocyte epithelial cells.
Nutrition in Acute and Chronic Pancreatitis
Published in Mary J. Marian, Gerard E. Mullin, Integrating Nutrition Into Practice, 2017
Treatment with pancreatic enzymes is thought to reduce pancreatic enzyme secretion and therefore reduce pain [43]. The presence of exogenous enzymes suppresses CCK release that prevents stimulation of endogenous pancreatic enzyme release [44]. However, there have been mixed results in clinical trials with some showing enzyme supplements are no better than placebo for the treatment of pain. Many different doses of enzymes supplements have been studied with no one dose showing increased benefit over any other dose [45]. Nonenteric-coated enzymes should be used with H2 blockers to prevent the activation of enzymes by stomach acid. Fecal chymotrypsin can be measured to assess response to pancreatic enzyme supplementation with decreasing quantities of chymotrypsin indicating adequate dosing [46].
Proteases, protease inhibitors and radiation carcinogenesis
Published in International Journal of Radiation Biology, 2023
Only a few of the BBIC human trials are discussed here. There was a Phase 1 trial in normal, healthy subjects (Lin et al. 2014), and some trials utilizing patients with: (A) oral leukoplakia (OL), a pre-malignant lesion. (Meyskens et al. 1999; Wan et al. 1999, Kennedy 2005; Armstrong et al. 2000a, 2000b), (B) benign prostatic hyperplasia (BPH) (Malkowicz et al. 1999, 2001; Kennedy and Wan 2002; Kennedy 2005), and (C) ulcerative colitis (UC) (Lichtenstein et al. 2002; Kennedy 2005; Lichtenstein et al. 2008). The doses used in these trials were measured in chymotrypsin inhibitory (C.I.) units, defined as the number of C.I. units that would be necessary to inhibit the activity of 1 mg of bovine pancreatic chymotrypsin (Kennedy et al. 1993). The safety and potential toxicity of BBIC were evaluated in all of the BBIC human trials performed and there were no toxic effects observed. Other results from some of the BBIC trials are described below.
Kolaviron modulates dysregulated metabolism in oxidative pancreatic injury and inhibits intestinal glucose absorption with concomitant stimulation of muscle glucose uptake
Published in Archives of Physiology and Biochemistry, 2023
Veronica F. Salau, Ochuko L. Erukainure, Neil A. Koorbanally, Md. Shahidul Islam
The pancreatic acinar cells play a vital role in the synthesis and secretion of chymotrypsin. The proteolytic degradation of membrane proteins by this protease which can be accelerated by oxidative stress has been implicated in the pathogenesis of pancreatic injuries. Chymotrypsin proteolytic activity has been correlated with increased MDA levels (lipid peroxidation) and tissue damage (Tonon et al.2013, Salau et al.2019a). The increased activity of chymotrypsin in the untreated pancreatic tissues (Figure 8(C)) indicates proteolysis resulting from induction of oxidative stress, and corroborates the increased level of MDA (Figure 6(D)). Treatment with kolaviron which led to decreased activity of chymotrypsin, therefore suggests its protective role against proteolysis in oxidative pancreatic injury.
Chymotrypsin attenuates adjuvant-induced arthritis by downregulating TLR4, NF-κB, MMP-1, TNF-α, IL-1β, and IL-6 expression in Sprague–Dawley rats
Published in Immunopharmacology and Immunotoxicology, 2022
Jianqiang Li, Linlin Wang, Guangting Zeng, Huilan Li, Jia Luo, Qijun Tian, Zanling Zhang
Therapy with proteolytic enzymes in rheumatic disorders has been used in previous studies [13]. Chintalacharuvu et al. [15] and Rovenská et al. [16] found the proteolytic enzyme drug Phlogenzym (bromelain, trypsin, rutin) had an inhibitory effect on collagen-induced arthritis in mice and rats, respectively. However, they did not explore the relevant mechanism further. Chymotrypsin is also a well-known proteolytic enzyme with anti-inflammatory effects [8]. The preliminary mechanism of chymotrypsin exerting an anti-rheumatic effect was studied in our research. We used CFA-induced rats as animal models in this study. Activated T cells could be detected, and multiple proinflammatory cytokines, such as TNF-α, IL-1β, IL-6, IL-17, and MMP were observed to participate in the pathological process of RA in an adjuvant-induced arthritis model [17].