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Pregastric Esterase
Published in Margit Hamosh, Lingual and Gastric Lipases: Their Role in Fat Digestion, 2020
Additional studies to assess the role of pregastric lipase in preruminant fat digestion suggest, however, that there might be no relationship between extent of lipolysis in the abomasum and milk utilization and weight gain.50 Russell et al. have examined abomasal fat digestion, retention of nitrogen and weight gain. These studies were carried out in abomasally cannulated calves during a sequence of 10 3-d periods beginning when the calves were 2 to 5 d old. Three calves were fed whole milk from nipple bottles to maximize release of pregastric esterase and two calves were fed by infusion into the abomasum to minimize exposure to the enzyme. Lipolytic activity and abomasal digestion were markedly higher in nipple-fed than in abomasalinfused animals (Figure 12). Digestibility, fat, protein and dry matter, nitrogen retention, and weight gain were, however, similar in the two groups of animals. The authors postulate that the surgical stress so early in life might have triggered the maturation of pancreatic exocrine function. It is clear that more research is needed to quantitate the contribution of pregastric esterase to the overall digestion of dietary fat. The characteristics of the enzyme, regulation of activity, and physiologic role are summarized in Table 10.
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Published in Calver Pang, Ibraz Hussain, John Mayberry, Pre-Clinical Medicine, 2017
Calver Pang, Ibraz Hussain, John Mayberry
This question looks at enzymes and enzyme regulation. It is important to be aware of how enzymes are regulated. Short-term regulation can be changes in substrate or product conformation, or changes in enzyme conformation (allosteric regulation, phosphorylation, proteolysis). Long-term regulation involves changes in rate of protein synthesis or degradation.
LIVER METABOLISM
Published in David M. Gibson, Robert A. Harris, Metabolic Regulation in Mammals, 2001
David M. Gibson, Robert A. Harris
terminal end of the protein that extends from the membrane of the endoplasmic retic ulum (figure 8.12). l ight transmembrane helices are sensitive to the concentration of cholesterol in the membrane. An increase in cholesterol can dampen the activity of this enzyme directly and enhance its rate of degradation. The cytosolic C-terminal segment harboring the catalytic site is also subject to phosphorylation (inactivation) by the AMP-activated protein kinase (bicyclic) system (Chapter 7). Regulation of gene expression ol this and the other synthetic enzymes, outlined in the next section, is the most stringent long-term mechanism of control. I IMG CoA reductase is a prime example of redundancy in enzyme regulation. Discovery of potent inhibitors of this enzyme has led to effective clinical management of deranged cholesterol homeostasis.
Larval and gut enzyme toxicity of n-hexane extract Epaltes pygmaea DC. against the arthropod vectors and its non-toxicity against aquatic predator
Published in Toxin Reviews, 2021
Kesavan Amala, Raja Ganesan, Sengodan Karthi, Sengottayan Senthil-Nathan, Muthiah Chellappandian, Patcharin Krutmunag, Narayanaswamy Radhakrishnan, Faruq Mohammad, Athirstam Ponsankar, Prabhakaran Vasantha-Srinivasan
Detoxifying enzymes are considered to be the major bio-marker for detecting the development of resistance in the insect pests (Lumjuan et al.2011). The metabolic functions of major detoxifying enzymes including α- and β-carboxylesterase were reduced. In contrast, the GST and CYP450 activity were increased in treated larvae (Thanigaivel et al.2017b). The active metabolites of botanicals deliver lethal activity to the gut epithelium cells leading to reduced metabolic function and irregular enzyme activity (Selin-Rani et al.2016). The sub-lethal dosage of NH-EPx significantly altered the larvae physiology by changing the regulation pattern of major gut enzymes of both the mosquito larvae. The major detoxifying enzymes like α and β- carboxylesterase, GST, and CYP450 of both Cx. quinquefasciatus and Ae. aegypti larvae were screened against the NH-EPx for its sub-lethal effects. The results illustrate that the active dosage of NH-EPx strongly inhibits the α and β-carboxylesterase level and increases the GST and CYP450 level in a dose-dependent manner in both the vectors. Similar to our results, Garcinia mangostana (L.) along with its active metabolite α-mangostin increases the activities of CYP450 and GST in Ae. aegypti larvae (Larson et al.2010). Our results were well supported by the previous investigations on the enzyme regulation pattern of mosquito vectors treated with different botanicals (Edwin et al.2016, Lija-Escaline et al.2015).
Body weight predicts Nicotinamide N-Methyltransferase activity in mouse fat
Published in Endocrine Research, 2018
Bianca Rudolphi, Benedikt Zapp, Nils A. Kraus, Franziska Ehebauer, Bettina J. Kraus, Daniel Kraus
It is currently unknown if and how NNMT activity is regulated, if not by the amount of NNMT itself. Our data do not show that NNMT expression predicts enzyme activity, which may indeed hint at enzyme regulation that is independent of protein expression. However, it is also possible that we did not detect a statistically significant relationship due to the small sample size. Using a radioactive enzyme activity assay, NNMT activity was once shown to depend on the amount of protein in human liver samples.37 Thus, analysis of NNMT protein expression currently appears to be a valid surrogate for enzyme activity. This may change if NNMT activity is found to be regulated allosterically or by post-translational modification.
Reliable chromatographic assay for measuring of indoleamine 2,3-dioxygenase 1 (IDO1) activity in human cancer cells
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2021
Ilona Sadok, Kamila Rachwał, Ilona Jonik, Magdalena Staniszewska
The primary finding showing IDO1 expression at the maternal–foetal interface and embryo implantation7 has started a series of studies on the role of IDO1 in several pathologies including neuropathology8, autoimmune disorders9, dermatological pathologies10, infections11, and cancer12. Although IDO1 expression and activity have been intensively studied in different diseases, many aspects of enzyme regulation still remain to be elucidated.