aroGand pheAgenes,encoding 3 Deoxy D arabinoheptulonate 7 phosphatesyn thase(DS) and Chorismate mutase (CM) prephenate dehydratase(PD) in the pathway of phenylalnine biosynthesisrespectively,were amplified by polymerase chain reaction(PCR) .The genes were assembled on the multicopy vectors and expressed in both Escherichia coli and Brevibacterium .The productsoftwogene weredetected by SDS PAGE.Theactivities ofrelevantenzymes were measuredinthecrudeextractofthe hoststrain. When aroG pheA genes...