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Orthomolecular Parenteral Nutrition Therapy
Published in Aruna Bakhru, Nutrition and Integrative Medicine, 2018
Arturo O'Byrne-Navia, Arturo O'Byrne-De Valdenebro
Cu is a functional component of many essential enzymes, known as copper enzymes or cuproenzymes (Harris 1997). Some important examples are: cytochrome C oxidase, lysyl oxidase, feroxidase, 2-furoate-CoA dehydrogenase, amine oxidase, catechol oxidase, tyrosinase, dopamine beta-monooxygenase, D-galaktozo oxidase, D-hexozo oxidoreductase, indole 2,3-dioxygenase, L-ascorbatoxidase, nitratreductase, peptidylglycine monooxygenase, flavonol 2,4-dioxygenase, superoxide dismutase (SOD), PHM (peptidylglycine monooxygenase hydroxylation), and others. Some physiological functions are dependent on the presence of these enzymes in the organism (Rolff and Tuczek 2008).
Plant Phenolics
Published in Ruth G. Alscher, John L. Hess, Antioxidants in Higher Plants, 2017
Four microsomal cytochrome P-450 dependent monooxygenases have been reported that catalyze formation of the various cinnamic-acid derivatives containing phenolic or catecholic functionalities. All require NAD(P)H (or other co-factors) and molecular oxygen for activity.21,45 Indeed, it is the introduction of the phenolic moieties by these enzymes that results in the antioxidant properties of the phen-ylpropanoids that are observed (see Section V). The aromatic hydroxylation enzymes (see Figure 4) include: (1) the monooxygenase, cinnamate-4-hydroxylase (E.C. 1.14.13.11) catalyzes the conversion of cinnamic acid 12 intop-coumaric acid 10,21 and has been detected in many different plant species and utilizes (trans) E-rather than (cis) Z-substrates; (2) a specific p-coumarate-3-hydroxylase from mung bean (Vigna mungo) seedlings catalyzes caffeic acid 7 formation;45 (3) phenolase (equivalent to polyphenol oxidase, tyrosinase, and catechol oxidase) also catalyzes caffeic acid 7 formation.21 Low substrate specificity (reviewed in Gross21), and the discovery of the mung bean, p-cοumarate-3-hydroxylase,45 requires a clarification of the relative importance of the specific P-coumarate-3-hydroxylase; and (4) ferulic acid-5-hydroxylase catalyzes the conversion of ferulic acid 11 into 5-hydroxyferulic acid 28, has only been detected in poplar (Populus deltoides x euramericana).46
Environmental post-processing increases the adhesion strength of mussel byssus adhesive
Published in Biofouling, 2018
Matthew N. George, Emily Carrington
Observed increases in plaque adhesion strength and work of adhesion are consistent with increases in the cohesive strength of the plaque protein network over time. At a seawater pH of 8.0, covalent cross-linking occurs between Mfps containing DOPA rich side chains. Cross-linking involves the incorporation of oxygen from the surrounding environment, and is further mediated by the enzyme catechol oxidase, which also displays peak activity at a pH of 8.0 (Waite 1985; Haemers et al. 2002). Oxidation of DOPA leads to the formation of DOPA-quinone, which forms covalent cross-links with DOPA, histidine, cysteine, and lysine (McDowell et al. 1999; Zhao and Waite 2006a; Miserez et al. 2010). The development of large quantities of DOPA-quinone in mussel adhesive was evidenced in this study by plaques that changed color as they aged, from a milky white to a dark-tan color over the course of 20 days, a process that has been referred to as quinone tanning (Brown 1950).
Histidine residues at the copper-binding site in human tyrosinase are essential for its catalytic activities
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2020
Hyangsoon Noh, Sung Jun Lee, Hyun-Joo Jo, Hye Won Choi, Sungguan Hong, Kwang-Hoon Kong
To date, two crystal structures of catechol oxidase9,10, three crystal structures of haemocyanin11–13, and three crystal structures of tyrosinase – from Agaricus bisporus14, Streptomyces castaneoglobisporus15, and Bacillus megaterium16 – have been resolved. Unfortunately, there is still no crystal structure of human tyrosinase; however, a reliable model could be generated based on the amino acid sequence and previously reported active sites17. The mature human tyrosinase consists of 529 amino acids including a short N-terminal signal peptide targeting the nascent polypeptide to the endoplasmic reticulum for folding, sorting, and, modification18. Further, it contains seven N-glycosylation motifs, two putative copper-coordinating sites distinct to CuA and CuB, one transmembrane domain, and a short carboxyl tail that has the important signals for targeting and sorting to melanosomes19. Moreover, six histidine residues in the active site are involved in coordination with the two copper ions (CuA and CuB)20. However, there is no clear evidence for the direct binding of human tyrosinase to copper. The alignment of amino acid sequence for tyrosinases, catechol oxidases, and haemocyanins suggested that the two homologous regions distinct to CuA and CuB could be directly involved in the two copper bindings, which are critical for the catalytic activities of the enzymes21. Furthermore, a mutational study of human tyrosinase revealed that both copper binding sites are necessary for the catalytic activity of the enzyme and for copper binding at the active site22.