Escherichia coli phenylalanine dehydrogenase

An improved process was also developed using phenylalanine dehydrogenase from T. intermedius expressed in Escherichia coli BL21 (DE3) (pPDHl 55K)... 

In bacteria and other micro-organisms, unlike higher organisms, L-phenylalanine (1) is not normally a precursor of L-tyrosine (2). Davis postulate that in these organisms prephenic acid is the precursor of L-tyrosine (2) and subsequent work at the enzymic level by Schwink and Adams established this proposal. Thus in Escherichia coli prephenic acid (31) is oxidatively aromatised to p-hydroxyphenylpyruvic acid (33) by a soluble, NAD" dependent, enzyme—prephenate dehydrogenase. With appropriate fortification —addition of L-glutamate and pyridoxal phosphate as cofactors —extracts of Escherichia coli then convert p-hydroxyphenylpyruvic acid quantitatively to L-tyrosine by transamination. 

Rec. Escherichia coli expressing modified phenylalanine dehydrogenase... 

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