Tarantula Hemocyanin Shows Phenoloxidase Activity

Decker, Heinz; Rimke, T.

doi:10.1074/jbc.273.40.25889

Cited by 205 publications

(148 citation statements)

References 24 publications

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“…These experimental observations suggest that CuðIIÞ 2 ðμ-η 2 ∶η 2 -O 2 2− Þ cores are intrinsically able to perform all of the CBC protein functions. Consistent with this hypothesis was the recent observation that partial denaturation or proteolytic digestion of hemocyanin induces monophenolase activity (14,15).…”

supporting

confidence: 67%

Structure/function correlations among coupled binuclear copper proteins through spectroscopic and reactivity studies of NspF

Ginsbach

Kieber‐Emmons

Nomoto

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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The terminal step of 4-hydroxy-3-nitrosobenzamide biosynthesis in Streptomyces murayamaensis is performed by NspF, a mono-oxygenase that converts o -aminophenols to the corresponding nitroso product (hydroxyanilinase activity). Previous biochemical characterization of the resting form of NspF suggested that this enzyme belonged to the coupled binuclear copper enzyme (CBC) family. Another member of this enzyme family, tyrosinase, is able to mono-oxygenate monophenols (monophenolase activity) but not o -aminophenols. To gain insight into the unique reactivity of NspF, we have generated and characterized the oxy form of its active site. The observation of spectral features identical to those of oxy-tyrosinase indicates that oxy-NspF contains a Cu 2 O 2 core where peroxide is coordinated in a μ - η 2 ∶ η 2 mode, confirming that NspF is a CBC enzyme. This oxy form is found to react with monophenols, indicating that, like tyrosinase, NspF also possesses monophenolase activity. A comparison of the two electrophilic mechanisms for the monophenolase and hydroxyanilinase activity indicates a large geometric change between their respective transition states. The potential for specific interactions between the protein pocket and the substrate in each transition state is discussed within the context of the differential reactivity of this family of enzymes with equivalent μ - η 2 ∶ η 2 peroxy bridged coupled binuclear copper active sites.

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supporting

confidence: 67%

Structure/function correlations among coupled binuclear copper proteins through spectroscopic and reactivity studies of NspF

Ginsbach

Kieber‐Emmons

Nomoto

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…If hemocyanins did evolve from phenoloxidases and tyrosinases the substrate binding capacity of the enzyme must have been inhibited without hindering O 2 binding. This seems to have been accomplished by the addition of residues blocking the active site to large substrates (17,23,24). Indeed, just such a difference has been noted by comparing the crystal structure of sweet potato catechol oxidase with that of molluscan hemocyanin (15).…”

Section: From What Did Hemocyanins Evolve?mentioning

confidence: 99%

Hemocyanins and Invertebrate Evolution

Holde

Miller

Decker

2001

Journal of Biological Chemistry

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303

187

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“…Under certain conditions, such as limited proteolysis or binding to small molecules (e.g., SDS), hemocyanins can be converted to enzymes displaying PO activities (30,31). Although o-di-PO activity of hemocyanins was observed most of the time (32), mono-oxygenase activity was observed from hemocyanins of a scorpion (33), a tarantula (34), and an octopus (35).…”

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confidence: 99%

Crystal structure of Manduca sexta prophenoloxidase provides insights into the mechanism of type 3 copper enzymes

Wang

Jiang

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

161

133

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Arthropod phenoloxidase (PO) generates quinones and other toxic compounds to sequester and kill pathogens during innate immune responses. It is also involved in wound healing and other physiological processes. Insect PO is activated from its inactive precursor, prophenoloxidase (PPO), by specific proteolysis via a serine protease cascade. Here, we report the crystal structure of PPO from a lepidopteran insect at a resolution of 1.97 Å, which is the initial structure for a PPO from the type 3 copper protein family. Manduca sexta PPO is a heterodimer consisting of 2 homologous polypeptide chains, PPO1 and PPO2. The active site of each subunit contains a canonical type 3 di-nuclear copper center, with each copper ion coordinated with 3 structurally conserved histidines. The acidic residue Glu-395 located at the active site of PPO2 may serve as a general base for deprotonation of monophenolic substrates, which is key to the ortho-hydroxylase activity of PO. The structure provides unique insights into the mechanism by which type 3 copper proteins differ in their enzymatic activities, albeit sharing a common active center. A drastic change in electrostatic surface induced on cleavage at Arg-51 allows us to propose a model for localized PPO activation in insects.innate immune ͉ tyrosinase ͉ melanization ͉ zymogen activation ͉ hemocyanin P henoloxidase (PO), a critical component of the innate immune system in insects and crustaceans, is present as a zymogen [prophenoloxidase (PPO)] in hemolymph and becomes activated on wounding or infection (1, 2). Possessing ohydroxylase (EC 1.14.18.1) and o-di-PO (EC 1.10.3.1) activities, PO converts a variety of monophenolic and o-diphenolic substrates to o-quinones (3). Quinones can act as cross-linkers for wound healing, and they also polymerize to form melanin capsules around parasites and parasitoids (4-6). Quinones and other reactive intermediates (e.g., 5,6-dihydroxyindole) directly kill microbial pathogens (7). Although PO-generated compounds are powerful weapons against pathogens, they could also cause damage to host tissues and cells. Consequently, the activation of PPO is mediated by a cascade of highly specific serine proteases and regulated as a local transient reaction against invading organisms (8).The proteolytic activation of PPO requires a trypsin-like serine protease, known as PPO activating protease (PAP) or PPO activating enzyme, which cuts the protein substrate next to an Arg residue near its amino-terminus (9-13). PAP contains regulatory clip domain(s) followed by a catalytic domain that hydrolyzes synthetic substrates at various ionic strengths and cleaves PPO in low-salt buffers preferably. In some insects, PAP generates active PO in the presence of an auxiliary factor consisting of clip-domain serine protease homolog (SPH), which lacks catalytic activity because of the substitution of the active site Ser by Gly (14,15). Unlike its precursor, active PO selfassociates into oligomers, binds to other proteins, and sticks to column matrices; consequently, it has n...

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Tarantula Hemocyanin Shows Phenoloxidase Activity

Cited by 205 publications

References 24 publications

Structure/function correlations among coupled binuclear copper proteins through spectroscopic and reactivity studies of NspF

Structure/function correlations among coupled binuclear copper proteins through spectroscopic and reactivity studies of NspF

Hemocyanins and Invertebrate Evolution

Crystal structure of Manduca sexta prophenoloxidase provides insights into the mechanism of type 3 copper enzymes

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