Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.10.3.1 (tyrosinase)
 9,065 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Menkes protein (ATP7A) is a P-type ATPase involved in copper uptake and homeostasis. Disturbed copper homeostasis occurs in patients with Menkes disease, an X-linked disorder characterized by mental retardation, neurodegeneration, connective tissue disorders, and early childhood death. Mutations in ATP7A result in malfunction of copper-requiring enzymes, such as tyrosinase and copper/zinc superoxide dismutase. The first step of the two-step amidation reaction carried out by peptidylglycine alpha-amidating monooxygenase (PAM) also requires copper. We used tissue from wild-type rats and mice and an ATP7A-specific antibody to determine that ATP7A is expressed at high levels in tissues expressing high levels of PAM. ATP7A is largely localized to the trans Golgi network in pituitary endocrine cells. The Atp7a mouse, bearing a mutation in the Atp7a gene, is an excellent model system for examining the consequences of ATP7A malfunction. Despite normal levels of PAM protein, levels of several amidated peptides were reduced in pituitary and brain extracts of Atp7a mice, demonstrating that PAM function is compromised when ATP7A is inactive. Based on these results, we conclude that a reduction in the ability of PAM to produce bioactive end-products involved in neuronal growth and development could contribute to many of the biological effects associated with Menkes disease.
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PMID:Menkes protein contributes to the function of peptidylglycine alpha-amidating monooxygenase. 1248 45

Reaction thermodynamics and potential energy surfaces are calculated using density functional methods to investigate possible reactive Cu/O(2) species for H-atom abstraction in peptidylglycine alpha-hydroxylating monooxygenase (PHM), which has a noncoupled binuclear Cu active site. Two possible mononuclear Cu/O(2) species have been evaluated, the 2-electron reduced Cu(II)(M)-OOH intermediate and the 1-electron reduced side-on Cu(II)(M)-superoxo intermediate, which could form with comparable thermodynamics at the catalytic Cu(M) site. The substrate H-atom abstraction reaction by the Cu(II)(M)-OOH intermediate is found to be thermodynamically accessible due to the contribution of the methionine ligand, but with a high activation barrier ( approximately 37 kcal/mol, at a 3.0-A active site/substrate distance), arguing against the Cu(II)(M)-OOH species as the reactive Cu/O(2) intermediate in PHM. In contrast, H-atom abstraction from substrate by the side-on Cu(II)(M)-superoxo intermediate is a nearly isoenergetic process with a low reaction barrier at a comparable active site/substrate distance ( approximately 14 kcal/mol), suggesting that side-on Cu(II)(M)-superoxo is the reactive species in PHM. The differential reactivities of the Cu(II)(M)-OOH and Cu(II)(M)-superoxo species correlate to their different frontier molecular orbitals involved in the H-atom abstraction reaction. After the H-atom abstraction, a reasonable pathway for substrate hydroxylation involves a "water-assisted" direct OH transfer to the substrate radical, which generates a high-energy Cu(II)(M)-oxyl species. This provides the necessary driving force for intramolecular electron transfer from the Cu(H) site to complete the reaction in PHM. The differential reactivity pattern between the Cu(II)(M)-OOH and Cu(II)(M)-superoxo intermediates provides insight into the role of the noncoupled nature of PHM and dopamine beta-monooxygenase active sites, as compared to the coupled binuclear Cu active sites in hemocyanin, tyrosinase, and catechol oxidase, in O(2) activation.
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PMID:Oxygen activation by the noncoupled binuclear copper site in peptidylglycine alpha-hydroxylating monooxygenase. Reaction mechanism and role of the noncoupled nature of the active site. 1508 Jul 5

Copper is an essential cofactor for approximately a dozen cuproenzymes in which copper is bound to specific amino acid residues in an active site. However, free cuprous ions react readily with hydrogen peroxide to yield the deleterious hydroxyl radical. Therefore, copper homeostasis is regulated very tightly, and unbound copper is extremely low in concentration. Copper imported by the plasma membrane transport protein Ctr1 rapidly binds to intracellular copper chaperone proteins. Atox1 delivers copper to the secretory pathway and docks with either copper-transporting ATPase ATP7B in the liver or ATP7A in other cells. ATP7B directs copper to plasma ceruloplasmin or to biliary excretion in concert with a newly discovered chaperone, Murr1, the protein missing in canine copper toxicosis. ATP7A directs copper within the transgolgi network to the proteins dopamine beta-monooxgenase, peptidylglycine alpha-amidating monooxygenase, lysyl oxidase, and tyrosinase, depending on the cell type. CCS is the copper chaperone for Cu,Zn-superoxide dismutase; it delivers copper in the cytoplasm and intermitochondrial space. Cox17 delivers copper to mitochondria to cytochrome c oxidase via the chaperones Cox11, Sco1, and Sco2. Other copper chaperones may exist and might include metallothionein and amyloid precursor protein (APP). Genetic and nutritional studies have illustrated the essential nature of these copper-binding proteins; alterations in their levels are associated with severe pathology.
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PMID:Intracellular copper transport in mammals. 1511 35

The considerable recent advances in copper-dioxygen coordination chemistry demonstrate the existence of a variety of dioxygen-derived Cu(n)-O(2) complexes, forming a basis for discussion of alternate oxidant types in copper chemistry and biochemistry. Peroxo complexes may react as nucleophilic reagents, and several types of electrophilic mono- or dicopper (hydro)peroxides exist. Side-on peroxo-dicopper(II) species effect aromatic hydroxylations, including phenolic substrates, in model systems and in the enzyme tyrosinase. Bis-micro-oxo-dicopper(III) entities are capable of hydrogen-atom abstraction reactions, or atom transfer to phosphines and sulfides. The scope and mechanisms of mononuclear Cu(II) superoxides or peroxides are yet to be established, but may be relevant to monooxygenases like peptidylglycine alpha-hydroxylating monooxygenase.
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PMID:Oxidant types in copper-dioxygen chemistry: the ligand coordination defines the Cu(n)-O2 structure and subsequent reactivity. 1531 36

Binuclear Cu proteins play vital roles in O(2) binding and activation in biology and can be classified into coupled and noncoupled binuclear sites based on the magnetic interaction between the two Cu centers. Coupled binuclear Cu proteins include hemocyanin, tyrosinase, and catechol oxidase. These proteins have two Cu centers strongly magnetically coupled through direct bridging ligands that provide a mechanism for the 2-electron reduction of O(2) to a mu-eta(2):eta(2) side-on peroxide bridged Cu(II)(2)(O(2)(2-)) species. This side-on bridged peroxo-Cu(II)(2) species is activated for electrophilic attack on the phenolic ring of substrates. Noncoupled binuclear Cu proteins include peptidylglycine alpha-hydroxylating monooxygenase and dopamine beta-monooxygenase. These proteins have binuclear Cu active sites that are distant, that exhibit no exchange interaction, and that activate O(2) at a single Cu center to generate a reactive Cu(II)/O(2) species for H-atom abstraction from the C-H bond of substrates. O(2) intermediates in the coupled binuclear Cu enzymes can be trapped and studied spectroscopically. Possible intermediates in noncoupled binuclear Cu proteins can be defined through correlation to mononuclear Cu(II)/O(2) model complexes. The different intermediates in these two classes of binuclear Cu proteins exhibit different reactivities that correlate with their different electronic structures and exchange coupling interactions between the binuclear Cu centers. These studies provide insight into the role of exchange coupling between the Cu centers in their reaction mechanisms.
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PMID:O2 activation by binuclear Cu sites: noncoupled versus exchange coupled reaction mechanisms. 1534 Jan 47

Copper-containing enzymes that react with O(2) play a key role in many biological processes. Mononuclear, dinuclear and trinuclear copper centers function in O(2) binding, activation and subsequent substrate oxidation. Recent advances in the structural biology of O(2)-activating copper enzymes range from the identification of novel copper centers, such as that of particulate methane monooxygenase, to the elucidation of the details of O(2) binding and reactivity in peptidylglycine alpha-hydroxylating monooxygenase. Structures of phenoxazinone synthase and Fet3 contribute to our understanding of multicopper oxidases. Additionally, details of the tyrosinase structure provide new insight into how dicopper sites confer substrate specificity. A common theme for each of these enzymes is that the protein scaffold plays a major role in dictating the overall function.
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PMID:Structural insights into dioxygen-activating copper enzymes. 1701 Nov 83

Copper is an essential trace element required by all aerobic organisms as a cofactor for enzymes involved in normal growth, development, and physiology. Ctr1 proteins are members of a highly conserved family of copper importers responsible for copper uptake across the plasma membrane. Mice lacking Ctr1 die during embryogenesis from widespread developmental defects, demonstrating the need for adequate copper acquisition in the development of metazoan organisms via as yet uncharacterized mechanisms. Whereas the fruit fly, Drosophila melanogaster, expresses three Ctr1 genes, ctr1A, ctr1B, and ctr1C, little is known about their protein isoform-specific roles. Previous studies demonstrated that Ctr1B localizes to the plasma membrane and is not essential for development unless flies are severely copper-deficient or are subjected to copper toxicity. Here we demonstrate that Ctr1A also resides on the plasma membrane and is the primary Drosophila copper transporter. Loss of Ctr1A results in copper-remedial developmental arrest at early larval stages. Ctr1A mutants are deficient in the activity of copper-dependent enzymes, including cytochrome c oxidase and tyrosinase. Amidation of Phe-Met-Arg-Phe-amides, a group of cardiomodulatory neuropeptide hormones that are matured via the action of peptidylglycine alpha-hydroxylating monooxygenase, is defective in neuroendocrine cells of Ctr1A mutant larvae. Moreover, both the Phe-Met-Arg-Phe-amide maturation and heart beat rate defects observed in Ctr1A mutant larvae can be partially rescued by exogenous copper. These studies establish clear physiological distinctions between two Drosophila plasma membrane copper transport proteins and demonstrate that copper import by Ctr1A is required to drive neuropeptide maturation during normal growth and development.
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PMID:Drosophila Ctr1A functions as a copper transporter essential for development. 1757 40