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The second Cupredoxin domain of phenoxazinone synthase (PHS) Phenoxazinone synthase (PHS, 2-aminophenol:oxygen oxidoreductase) catalyzes the oxidative coupling of substituted o-aminophenols to produce phenoxazinones. PHS participates in diverse biological functions such as spore pigmentation and biosynthesis of the antibiotic grixazone. It is a member of the multicopper oxidase (MCO) family, which couples the oxidation of a substrate with a four-electron reduction of molecular oxygen to water. Although MCOs have diverse functions, majority of them have three cupredoxin domain repeats that include one mononuclear and one trinuclear copper center. The copper ions are bound in several sites: Type 1, Type 2, and/or Type 3. The ensemble of types 2 and 3 copper is called a trinuclear cluster. MCOs oxidize their substrate by accepting electrons at a mononuclear copper center and transferring them to the active site trinuclear copper center. The cupredoxin domain 2 of 3-domain MCOs has lost the ability to bind copper. |
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