Structures and Functions of the Phenolase Complex

Hs, Mason

doi:10.1038/177079a0

Cited by 190 publications

(42 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…[1] The so-called type 3 copper proteins have an antiferromagnetically coupled dicopper core with three histidine ligands on each copper ion and mhydroxo bridging in the met-Cu II -Cu II form, which results in an EPR-silent active site. Well-known representatives of type 3 copper proteins are hemocyanin, the dioxygen carrier and transport protein for arthropods and molluscs, [2,3] tyrosinase, which catalyzes the hydroxylation of phenols to catechols (cresolase activity) and the oxidation of catechols to quinones (catecholase activity), [4] and catechol oxidase (CO) that exhibits only catecholase activity. CO was first isolated by Kubowitz in 1937 from potatoes.…”

Section: Introductionmentioning

confidence: 99%

Less Symmetrical Dicopper(II) Complexes as Catechol Oxidase Models—An Adjacent Thioether Group Increases Catecholase Activity

Merkel

Möller

Piacenza

et al. 2005

Chemistry A European J

124

View full text Add to dashboard Cite

Three new unsymmetrical compartmental dinucleating ligands, 4-bromo-2-(4-methylpiperazin-1-ylmethyl)-6-[{2-(1-piperidyl)ethyl}aminomethyl]phenol (HL1), 4-bromo-2-(4-methylpiperazin-1-ylmethyl)-6-[{2-(morpholin-4-yl)ethyl}aminomethyl]phenol (HL2), and 4-bromo-2-(4-methylpiperazin-1-ylmethyl)-6-[{2-(thiomorpholin-4-yl)ethyl}aminomethyl]phenol (HL3), have been synthesized in order to model the active site of type 3 copper proteins. The dicopper(II) complexes of these ligands give first hints about the influence of a thioether group close to the metal site. The bromophenol-based ligands have one piperazine arm and one other bidentate arm in positions 2 and 6 of the phenolic ring, respectively. With each ligand a dinuclear copper(II) complex was prepared and structurally characterized. The copper ions were found to have square pyramidal environments and a mixture of endogenous phenoxo and exogenous acetate bridging. The influence of a heteroatom in one arm of the ligand on catecholase activity and speciation in solution was studied by UV/Vis spectroscopy, ESI-MS experiments and, DFT calculations.

show abstract

Section: Introductionmentioning

confidence: 99%

Less Symmetrical Dicopper(II) Complexes as Catechol Oxidase Models—An Adjacent Thioether Group Increases Catecholase Activity

Merkel

Möller

Piacenza

et al. 2005

Chemistry A European J

124

View full text Add to dashboard Cite

show abstract

“…In plants, the most common precursor is just catechol (Figure 1(e)); so the melanin formed is also named catechol-melanin [8,32] and the enzymatic system involved in the synthesis is named catechol oxidase [93]. Tyrosine is a poor substrate of these catechol oxidases, but it should be clear that catechol-melanin is a subtype of allomelanin, and catechol oxidase which is the most frequent type of plant phenol oxidases [94], related to animal tyrosinases.…”

Section: Plant Melaninmentioning

confidence: 99%

Melanins: Skin Pigments and Much More—Types, Structural Models, Biological Functions, and Formation Routes

Solano

2014

New Journal of Science

443

431

View full text Add to dashboard Cite

This review presents a general view of all types of melanin in all types of organisms. Melanin is frequently considered just an animal cutaneous pigment and is treated separately from similar fungal or bacterial pigments. Similarities concerning the phenol precursors and common patterns in the formation routes are discussed. All melanins are formed in a first enzymatically-controlled phase, generally a phenolase, and a second phase characterized by an uncontrolled polymerization of the oxidized intermediates. In that second phase, quinones derived from phenol oxidation play a crucial role. Concerning functions, all melanins show a common feature, a protective role, but they are not merely photoprotective pigments against UV sunlight. In pathogenic microorganisms, melanization becomes a virulence factor since melanin protects microbial cells from defense mechanisms in the infected host. In turn, some melanins are formed in tissues where sunlight radiation is not a potential threat. Then, their redox, metal chelating, or free radical scavenging properties are more important than light absorption capacity. These pigments sometimes behave as a doubleedged sword, and inhibition of melanogenesis is desirable in different cells. Melanin biochemistry is an active field of research from dermatological, biomedical, cosmetical, and microbiological points of view, as well as fruit technology.

show abstract

“…Whereas aminochromes are formed via intra-molecular cyclization of catecholamine o-quinone (dopachrome from o-dopaquinone, adrenochrome from epinephrine oquinone), the aminoquinones and topaquinones are formed by the addition of nitrogenous compounds and water, respectively, to o-quinones (66,(107)(108)(109).…”

Section: Reactions Of O-semiquinonesmentioning

confidence: 99%

Semiquinone Anion Radicals of Catechol(amine)s, Catechol Estrogens, and Their Metal Ion Complexes

Kalyanaraman¹,

Felix²,

Sealy³

1985

Environmental Health Perspectives

View full text Add to dashboard Cite

The characterization and identification of semiquinone radicals from catechol(amine)s and catechol estrogens by electron spin resonance spectroscopy is addressed. The use of diamagnetic metal ions, especially Mg2e and Zn2+ ions, to detect transient semiquinone radicals in biological systems and to monitor their reactions, is discussed. A brief account of the identification and reactions of quinones is also presented.

show abstract

Structures and Functions of the Phenolase Complex

Cited by 190 publications

References 18 publications

Less Symmetrical Dicopper(II) Complexes as Catechol Oxidase Models—An Adjacent Thioether Group Increases Catecholase Activity

Less Symmetrical Dicopper(II) Complexes as Catechol Oxidase Models—An Adjacent Thioether Group Increases Catecholase Activity

Melanins: Skin Pigments and Much More—Types, Structural Models, Biological Functions, and Formation Routes

Semiquinone Anion Radicals of Catechol(amine)s, Catechol Estrogens, and Their Metal Ion Complexes

Contact Info

Product

Resources

About