Engineering a Cytochrome P450 for Demethylation of Lignin-Derived Aromatic Aldehydes.

Biological funneling of lignin-derived aromatic compounds is a promising approach for valorizing its catalytic depolymerization products. Industrial processes for aromatic bioconversion will require efficient enzymes for key reactions, including demethylation of -methoxy-aryl groups, an essential and often rate-limiting step. The recently characterized GcoAB cytochrome P450 system comprises a coupled monoxygenase (GcoA) and reductase (GcoB) that catalyzes oxidative demethylation of the methoxy-aryl group in guaiacol.

How Chemical Environment Activates Anthralin and Molecular Oxygen for Direct Reaction.

The role of the chemical environment in promoting anthralin/O reactions was discovered using neat solvents to model the amino acids of a cofactor-independent oxygenase. Experimental and computational results highlight the importance of the substrate-enolate, which is accessed via energetically small, escalating steps in which the ground-state keto-isomer is tautomerized to an enol and then ionized by solvent. The resulting ion-pair is poised for spontaneous electron transfer to O.

How a cofactor-free protein environment lowers the barrier to O reactivity.

Molecular oxygen (O)-utilizing enzymes are among the most important in biology. The abundance of O, its thermodynamic power, and the benign nature of its end products have raised interest in oxidases and oxygenases for biotechnological applications. Although most O-dependent enzymes have an absolute requirement for an O-activating cofactor, several classes of oxidases and oxygenases accelerate direct reactions between substrate and O using only the protein environment.