| Summary: | 2,5-dihydroxyacetanilide epoxidase from Streptomyces LL-C10037 (DHAE I)
catalyzes the epoxidation of hydroquinone 4, to form epoxyquinone 7. DHAE I has been
purified to homogeneity, with an overall purification factor greater than 23,000. N-terminal
and internal amino acid sequences have been obtained from the purified enzyme so
that the epoxidase gene may be cloned by using reverse genetics.
The epoxidation reaction of DHAE I requires only molecular oxygen and no added
cofactors. The detailed chemical mechanism has been elucidated using isotopically labeled
oxygen. DHAE I is a dioxygenase belonging to a new and unrecognized class of
dioxygenases that are described as "hydroquinone epoxidizing dioxygenases."
DHAE I and another epoxidizing enzyme which acts on the same substrate but
producing the enantiomeric epoxide, DHAE II from Streptomyces MPP 3051, have had
their active sites examined for structural latitude. DHAE II shows more flexibility toward
substrate analogs than DHAE I. However, both enzymes are very specific for the correct
substrate. From these studies, crude three dimensional models of the two active sites have
been constructed. === Graduation date: 1998
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