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Laccases contain a blue mononuclear copper center known as 'type-1', and thought to be the primary electron acceptor from organic substrates during the catalytic cycle. A small group of laccases are also known that lack the 600 nm band and hence the blue color ("yellow laccases"). We report on the use of semiempirical (ZINDO/S-CI) calculations in order to simulate UV-vis spectral parameters for the laccase type 1 copper, attempting to assign geometrical and electronic structure elements that may control the color of this site. The ~600-nm band of the type 1 copper is confirmed to arise mainly from sulfur-to-copper charge transfer, and strong distortions allowing for its displacement by more than 200 nm and/or its dissolution are identified. [ABSTRACT FROM AUTHOR]

The cytochromes P450 are hemoproteins that catalyze a range of oxidative C-H functionalization reactions, including aliphatic and aromatic hydroxylation. These transformations are important in a range of biological contexts, including biosynthesis and xenobiotic biodegradation. Much work has been carried out on the mechanism of aliphatic hydroxylation, implicating hydrogen atom abstraction, but aromatic hydroxylation is postulated to proceed differently. One mechanism invokes as the key intermediate an arene oxide (and/or its oxepin tautomer). Conclusive isolation of this intermediate has remained elusive and, currently, direct formation of phenols from a Meisenheimer intermediate is believed to be favored. We report here the identification of a P450 [P450cam (CYP101A1) and P450cin (CYP176A1)]-generated arene oxide as a product of in vitro oxidation of tert-butylbenzene. Computations (CBS-QB3) predict that the arene oxide and oxepin have similar stabilities to other arene oxides/oxepins implicated (but not detected) in P450-mediated transformations, suggesting that arene oxides can be unstable terminal products of P450-catalyzed aromatic oxidation that can explain the origin of some observed metabolites., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)