Formation in vitro of the 3,4,6-trihydroxyphenylalanine quinone cofactor.

An Escherichia coli K-12 2-phenylethylamine oxidase gene with a mutated leader sequence region produced a largely inactive form of the enzyme in the cytoplasm. This form of the enzyme was activated 30-50-fold on incubation at 30 degrees C in the absence of any added cofactors. After activation the enzyme contained a quinone which was not detected in the non-activated form. This is the first report of the formation in vitro of any quinoenzyme cofactor.