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Structural Organization of the Liver
Published in Robert G. Meeks, Steadman D. Harrison, Richard J. Bull, Hepatotoxicology, 2020
Biochemical studies on subcellular fractions that led to the discovery of lysosomes also identified another class of membrane-bound organelle containing enzymes that catalized reactions involving hydrogen peroxide, and hence have been termed peroxisomes (deDuve and Baudhuin, 1966). Three of these catalyzing enzymes produce hydrogen peroxide (Urate oxidase, d-amino acid oxidase and α-hydroxy acid oxidase) and one (catalase) destroys it. Electron microscopy of isolated peroxisomes proved that they were indeed the microbodies described earlier by Rouiller and Bernhard (1956).
Free radicals in biology
Published in Roger L. McMullen, Antioxidants and the Skin, 2018
In general, enzymes can be sources of free radicals as they are often involved in electron transfer reactions, which occasionally result in the leakage of electrons.2 In addition, various enzymes that serve roles as oxidases can potentially be sources of free radical species. Several examples include: D-amino acid oxidase: This enzyme is responsible for the eradication of unwanted amino acids in the cell.Xanthine oxidase: As part of purine metabolism, the degradation of hypoxanthine to xanthine and xanthine to uric acid is achieved by xanthine oxidase (Chapter 3).Nitric oxide synthase: Actually, this is a family of enzymes that is responsible for the synthesis of NO•.Myeloperoxidase: During phagocytosis (already discussed) this enzyme is responsible for the formation of HOCl.NADPH oxidase: As a membrane-bound protein, this enzyme participates in the production of O2•− during phagocytosis.
Biology and Distribution of Venomous Snakes of Medical Importance and The Composition of Snake Venoms
Published in Jürg Meier, Julian White, Handbook of: Clinical Toxicology of Animal Venoms and Poisons, 2017
The yellow colour of many snake venoms is due to riboflavin, which is present in the form of flavine mononucleotide (FMN) and forms the prosthetic group of venom L-amino acid oxidase171,172. Recently, it has been shown that the L-amino acid oxidase present in many snake venoms has antibacterial activity 173,174.
Prediction of novel inhibitors for Crotalus adamanteus
l -amino acid oxidase by repurposing FDA-approved drugs: a virtual screening and molecular dynamics simulation investigation
Published in Drug and Chemical Toxicology, 2021
Mostafa Khedrinia, Hassan Aryapour, Manijeh Mianabadi
Snakes venom are complex mixtures of enzymatic and non-enzymatic proteins, organic and inorganic compounds (Ramos and Selistre-De-Araujo 2006). One of these enzymes is l-amino acid oxidase (LAAO) with the systematic name of l-amino-acid: oxygen oxidoreductase (EC: 1.4.3.2), which is widely found in various organisms such as insects (Ahn et al.2000), fungus (Nuutinen et al.2012), bacteria (Geueke and Hummel 2002, Yu and Qiao 2012, Matsui et al.2014), plants (Cooper and Pinto 2005, Yang et al.2012), algae (Schriek et al.2009), mammals (Nakano and Danowski 1965, Puiffe et al.2013), and snakes (Li et al.1994, Du and Clemetson 2002, Samel et al.2006, 2008, Costa et al.2014, Izidoro et al.2014). l-Amino acid oxidase catalyzes the oxidative deamination of the l-type enantiomer of amino acids to produce ammonia and α-keto acid via an intermediate imino acid (in accordance with the following reaction) (Bordon et al.2015).
Quantitative proteomic analysis of venom from Southern India common krait (Bungarus caeruleus) and identification of poorly immunogenic toxins by immune-profiling against commercial antivenom
Published in Expert Review of Proteomics, 2019
Aparup Patra, Abhishek Chanda, Ashis K. Mukherjee
The enzymatic activities and pharmacological properties of SI B. caeruleus venom were assessed at a fixed amount of SI B. caeruleus venom protein (10 µg). L-kynurenine was used as a substrate for assaying L-amino acid oxidase (LAAO) activity, as described previously [20,32]. The ATPase, ADPase, and AMPase activities of SI B. caeruleus venom were assayed using ATP, ADP, and AMP, respectively, as substrates. One unit of ATPase/ADPase/AMPase activity was defined as micromoles of Pi released per min at 37°C [20]. Hyaluronidase activity was assayed by the turbidometric method, according to the protocol of Pukrittayakamee et al. (1988) [33] with slight modification, as described by Kalita et al. (2017) [26]. One unit of hyaluronidase activity was defined as a 1% decrease in turbidity, compared to the control, and activity was expressed as U/mg protein. A turbidometric method using egg yolk as substrate was used to assay phospholipase A2 (PLA2) activity [34,35], where one unit of PLA2 activity was arbitrarily defined as a 0.01 decrease in absorbance at 740 nm after 10 min of incubation [34,35].
The roles of hydrogen sulfide in renal physiology and disease states
Published in Renal Failure, 2022
Jianan Feng, Xiangxue Lu, Han Li, Shixiang Wang
Although originally viewed as only a toxic gas, H2S is now recognized as a gaseous signaling molecule that is in some ways similar to nitric oxide (NO) and carbon monoxide (CO) [7]. Unlike NO and CO, H2S is acidic, which allows it to dissolve in water. In addition, because H2S is highly lipophilic, it can spread freely to the cell membranes of all cell types [8]. The enzymes responsible for the generation of endogenous H2S include cystathionine–β–synthase (CBS), cystathionine–γ–lyase (CSE), and mitochondrial 3–mercaptopyruvate sulfurtransferase (3–MST) [9]. CBS and CSE both produce endogenous H2S in the cytosol, while 3–MST produces endogenous H2S in mitochondria [4,10]. Endogenous H2S is produced in four main ways. In the first mechanism, L–homocysteine and serine produce L–cystathionine under the action of CBS; the L–cystathionine is then changed into L–cysteine by CSE. Finally, H2S is formed in a process mediated by CBS and CSE in the cytoplasm [6]. In the second mechanism CSE reacts with L–homocysteine to produce H2S, α–ketobutyrate and L–homolanthionine [4]. In the third mechanism, cysteine aminotransferase converts L–cysteine to 3–mercaptopyruvate (3–MP), which is then utilized by 3–MST for the production of H2S in mitochondria [11]. In the final mechanism, D–amino acid oxidase mediates the transformation of D–cysteine to 3–MP, and H2S is subsequently produced under the action of 3–MST. It is worth noting that 3–MP needs to be imported to mitochondria for the next step. In the kidneys, the main substrate for H2S production is D–cysteine, and H2S from D–cysteine is much more abundant than that from L–cysteine [12] (Figure 1).