3,4-Dihydroxyphenylalanine (DOPA) is not a preferred substrate of Rhus vernicifera laccase, as rate constants for the anaerobic reduction of the type 1 cupric atom by l-DOPA (6.3 × 101 m-1 s-1), d-DOPA (2.6 × 101 m-1 s-1), and l-DOPA methyl ester (2.6 × 101 m-1 s-1) are considerably smaller than k1(catechol) (7 × 102 m-1 s-1) and rate constants characteristic of numerous other nonphysiological organic substrates (25 °C, pH 7.0, I = 0.5 m). The reactions of DOPA derivatives with laccase are unique, however, in that a two-term rate law pertains: kobsd = k0 + k1[phenol]; k0(l-DOPA) = 7 × 10-2 s-1. The reactivities of other catechol derivatives (pyrogallol, gallic acid, and methyl gallate) with laccase type 1 copper were also examined.
ASJC Scopus subject areas
- Molecular Biology