199mHg-derivatives of ascorbate oxidase and laccase: selective depletion and blocking of Cu-sites

We report on the^199mHg nuclear quadrupole interaction (NQI) of Hg-derivatives of the blue oxidases ascorbate oxidase (AO) and laccase (LAC). For fully reconstituted enzymes, three different NQIs were observed. The assignment of these NQIs to the type-1, -2, and -3 Cusites is based on type-2 depleted AO, on blocking studies with inactive Hg prior to^199mHg/carrier reconstitution, and on the population ratio observed for fully reconstituted LAC. The NQIs for both enzymes are similar, suggesting similar Cu-sites. The type-2 site is preferentially reconstituted, contrary to expectations. Neither the blocking nor the depletion is as selective as expected.