Expression of the Escherichia Coli TdcB gene encoding threonine dehydratase in L-isoleucine-overproducing Corynebacterium Glutamicum Yilw

Threonine dehydratase (EC 4.3.1.19, TDH) catalyzing the degradation of Thr to α-ketobutyrate, is a rate-limiting enzyme in L-Ile pathway. The tdcB gene encoding TDH was obtained from Escherichia coli K12 by PCR and expressed at E. coli BL21 (DE3). Then the tdcB gene was inserted into the shuttle expression vector pXMJ19 and the recombinant plasmid was electroporated into the L-isoleucine-producing strain of Corynebacterium glutamicum YILW. Crude extracts of the microbial strain containing the plasmid pXMJ19 tdcB retained 60% of the original TDH activity even in the presence of 300 mM L-Ile. The recombinant strain of bacteria showed 7.5% higher enzyme activity and 11.3% higher L-Ile production compared to the original strain.