کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
31569 | 44819 | 2012 | 9 صفحه PDF | دانلود رایگان |
Threonine dehydratase and acetohydroxy acid synthase are critical enzymes in the l-isoleucine biosynthesis pathway of Corynebacterium glutamicum, but their activities are usually feedback-inhibited. In this study, we characterized a feedback-resistant threonine dehydratase and an acetohydroxy acid synthase from an l-isoleucine producing strain C. glutamicum JHI3-156. Sequence analysis showed that there was only a single amino acid substitution (Phe383Val) in the feedback-resistant threonine dehydratase, and there were three mutated amino acids (Pro176Ser, Asp426Glu, and Leu575Trp) in the big subunit of feedback-resistant acetohydroxy acid synthase. The mutated threonine dehydratase over-expressed in E. coli not only showed completely resistance to l-isoleucine inhibition, but also showed enhanced activity. The mutated acetohydroxy acid synthase over-expressed in E. coli showed more resistance to l-isoleucine inhibition than the wild type. Over-expression of the feedback-resistant threonine dehydratase or acetohydroxy acid synthase in C. glutamicum JHI3-156 led to increase of l-isoleucine production; co-expression of them in C. glutamicum JHI3-156 led to 131.7% increase in flask cultivation, and could produce 30.7 g/L l-isoleucine in 72-h fed-batch fermentation. These results would be useful to enhance l-isoleucine production in C. glutamicum.
► Mutant TD and AHAS from JHI3-156 were characterized.
► Mutant TD was 100% resistant to l-isoleucine inhibition.
► The activity of mutant TD was enhanced in the presence of l-isoleucine.
► Overexpression of mutant TD or AHAS increased l-isoleucine production.
► l-isoleucine could reach 30.7 g/L when mutant TD and AHAS co-expressed.
Journal: Metabolic Engineering - Volume 14, Issue 5, September 2012, Pages 542–550