Molecular Design of Metalloproteins

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The aromatic hydroxylation is one of the hard oxidations to proceed and we have designed a myoglobin mutant which is able to oxidize aromatic ring on the basis of the following strategies 1)Introduction of the substrate, tryptophan, at the position of phenyl alanine 43.2)Replacement of histidine 64 by asparitic acid to allow rapid reaction of the mutant with hydrogen peroxide. At the same time, Valine 68 was also replaced by isoleucine to allow hydrogen peroxide readily accessing to the active site, The oxidative modification of the protein was monitored by ESI-TOF mass measurements. Upon the addition of 1 eq. of hydrogen peroxide, 16Da increase of the molecular weight was observed. Further addition of hydrogen peroxide afforded secondary product exhibiting 32Da increase of its mass. After the digestion of the protein, a fragment including W43 was purified and characterized by MALDI TOF mass and NMR. The modified residue was W43 having 6-hydroxide. This is the first example of aromatic hydroxylation by a stoichiometric amount of hydrogen peroxide. In addition, the secondary product was characterized as 2,6-dioxo-derivative of tryptophan 43.