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Macronutrients
Published in Chuong Pham-Huy, Bruno Pham Huy, Food and Lifestyle in Health and Disease, 2022
Chuong Pham-Huy, Bruno Pham Huy
Conjugated proteins or Heteroproteins consist of a simple protein combined with a nonprotein component. The nonprotein component is called a prosthetic group (36, 47). A protein without its prosthetic group is called an apoprotein. A protein molecule combined with its prosthetic group forms a heteroprotein. Prosthetic groups play an important role in the function of proteins. Conjugated proteins are classified according to the nature of their prosthetic groups. They include glycoproteins, lipoproteins, metalloproteins, hemoproteins, phosphoproteins, and so on. Glycoproteins contain a carbohydrate component. Lipoproteins are proteins containing lipid molecules such as cholesterol which are divided into High-Density Lipoprotein (HDL) or ‘good’ cholesterol and Low-Density Lipoprotein (LDL) or ‘bad’ cholesterol. Metalloproteins contain metal ions (iron, calcium, copper, zinc, and molybdenum). Phosphoproteins contain phosphate groups, while hemoproteins or chromoproteins possess heme groups such as hemoglobin. Hemoglobin is the metalloprotein containing iron for the transport of oxygen in the red blood cells of all mammals (36, 47).
Antigens
Published in Constantin A. Bona, Francisco A. Bonilla, Textbook of Immunology, 2019
Constantin A. Bona, Francisco A. Bonilla
Several mechanisms may lead to alterations in antigen structure and interaction with antibody. Genetic mutations leading to amino acid substitutions may alter structure in three ways: changing a contact residue; creating or destroying a glycosylation signal sequence; or altering higher order structure (Figure 3–10). The binding of metal or organic prosthetic groups important for the function of the antigen often alter structure. For example, some antibodies binding metmyoglobin (containing heme) do not bind apomyoglobin (without heme).
Reactivities of Amino Acids and Proteins with Iodine
Published in Erwin Regoeczi, Iodine-Labeled Plasma Proteins, 2019
Stearylcoenzyme A desaturase, a microsomal enzyme, catalyzes the formation of mon- ounsaturated fatty acids in the liver, and it contains 24 tyrosyl residues. Nitration (tetrani- tromethane) of one to two residues decreases the enzymic activity by 83%. Complete inactivation is observed after nitrating two to five residues, or acetylating (acetic anhydride) four. The effect is not reversed by hydroxylamine. Both types of modification cause a loss of the iron prosthetic group from the protein.354
Novel targets and inhibitors of the Mycobacterium tuberculosis cytochrome bd oxidase to foster anti-tuberculosis drug discovery
Published in Expert Opinion on Drug Discovery, 2023
Amaravadhi Harikishore, Vikneswaran Mathiyazakan, Kevin Pethe, Gerhard Grüber
Electrons, shuttled by MKH2 to the Mtb cyt-bd, are used to reduce oxygen to water within the catalytic center of subunit CydA. The mycobacterial cyt-bd structure reveals a pseudo-symmetrical arrangement of CydA and CydB subunits [42,43]. The subunits each consist of nine transmembrane helices which are clustered into two four-helix bundles and a periphery helix (Figure 2a) [42,43]. CydA contains the three heme prosthetic groups – low-spin heme b558, high-spin heme b595 and chlorin-type heme d arranged in a triangular fashion (Figure 2b). The inter heme distances between the respective hemes are approximately 15.6 Å (heme b558 to heme b595), 11.6 Å (heme b595 to heme d) and 19.0 Å (heme b558 to heme d). The prosthetic groups are associated with axial ligands that are conserved across species: H185 and M344 ligated as 5th and 6th ligand to heme b585, respectively. Amino acid E396 was bound to heme b595 as 5th ligand, while residue H18 forms the 5th ligand, and the dioxygen forms the 6th ligand at heme d. The inter heme distances coupled with the conservation of axial ligands across species point toward a sequential transfer of electrons from heme b558 followed by b595 and heme d in Mtb (Figure 2b) [42,44,45].
Molecular effects of ozone on amino acids and proteins, especially human hemoglobin and albumin, and the need to personalize ozone concentration in major ozone autohemotherapy
Published in Critical Reviews in Clinical Laboratory Sciences, 2023
Fouad Mehraban, Arefeh Seyedarabi
Hb is a tetrameric macromolecule consisting of two alpha subunits (7-helices) and two beta subunits (8-helices) that are structurally similar and have approximately the same molecular weight (141 to 146 amino acids). Each subunit contains a heme attachment pocket (prosthetic group) made of E and F helices (containing hydrophobic amino acids) located close to the surface of the Hb molecule. The heme inside this envelope has an iron atom in the center with four connections coordinated by the nitrogen atoms of the porphyrin ring. The iron atom is covalently attached to the proximal histidine (His F8) of Hb, and this structure allows the covalent attachment of oxygen and other gases to the iron in the heme of Hb. Distal histidine (His E7) also stabilizes bound oxygen by hydrogen bonding interaction. The prosthetic groups are active centers for the binding and transport of oxygen [80,81].
Zinc abrogates anticancer drug tamoxifen-induced hepatotoxicity by suppressing redox imbalance, NO/iNOS/NF-ĸB signaling, and caspase-3-dependent apoptosis in female rats
Published in Toxicology Mechanisms and Methods, 2020
Ademola C. Famurewa, Chima A. Ekeleme-Egedigwe, Ebuka E. David, Chinedum O. Eleazu, Abiola M. Folawiyo, Nwogo A. Obasi
Zinc is an essential micronutrient for all species. It is a component for tissue structure and serves as the prosthetic group of about 3000 proteins (Karweina et al. 2015). Zinc is a trace element involved in signaling, neurotransmission, immune response, fertility, growth, and development (Sharma et al. 2013). Robust body of evidence has shown that Zn possesses antioxidant and anti-inflammatory properties (Amara et al. 2008; Morshedi et al. 2014; Soussi et al. 2018) and maintains the redox balance by modulating several Zn-dependent enzymes such as superoxide dismutase, matrix metalloproteinases, Nrf2, and many other oxido-reductases (Maremanda et al. 2014). For example, Zn combats free radicals by preserving thiols, inhibiting NADPH oxidases, and stabilizing superoxide dismutase activity (Rahman 2007; Chasapis et al. 2012). Also, Zn acts as a potent NF-κB activation antagonist and suppresses TNF-α protein expression (Yamaguchi and Weitzmann 2011). Currently, some studies have reported the beneficial effect of Zn against toxicity of cyclophosphamide and methotrexate in testis (Maremanda et al. 2014; Lu et al. 2015; Maremanda and Jena 2017). Also, a number of natural antioxidant compounds have shown efficacy in TAM hepatotoxicity (Albukhari et al. 2009; El-Beshbishy et al. 2010; Suddek 2014a, 2014b), and the hepatoprotective effect of Zn, an established supplement with a wide physiological functions, in TAM hepatotoxicity has not been reported in the existing literature. Therefore, the study was designed to explore the possible role of Zn supplementation against TAM-induced hepatotoxicity and the associated mechanism in Wistar female rats.