Feedback-resistant homoserine transsuccinylases having a modified c-terminus
View Patent ↗The invention relates to a homoserine transsuccinylase, which exhibits reduced sensitivity towards L-methionine or SAM in comparison with a homoserine transsuccinylase wild-type enzyme, whereby the latter comprises an amino acid sequence containing a TyrGlnXaaThrPro sub-sequence, the Thr of said sub-sequence lying between positions 285 and 310 of the amino acid sequence and position 1 being filled by the starter methionine. The inventive homoserine transsuccinylase is characterized in that in comparison with the wild-type enzyme at least 2 amino acids are modified, said modification taking place in the Thr of the sub-sequence or in the C-terminal.
1. A homoserine transsuccinylase which, as compared with a homoserine transsuccinylase wild-type enzyme, exhibits a reduced sensitivity toward L-methionine or S-Adenosylmethionine (SAM), with the wild-type enzyme possessing an amino acid sequence of SEQ ID NO: 2 which comprises a constituent sequence TyrGlnXaaThrPro, with the Thr of this constituent sequence at position 297 onward being replaced by one of the mutations listed in Table 1.
2. A homoserine transsuccinylase as claimed in claim 1 , wherein it exhibits a change of at least 5 amino acids.
3. A homoserine transsuccinylase as claimed in claim 1 , wherein it exhibits a resistance toward the inhibitors SAM and/or L-methionine which is increased (increased Ki) at least 2-fold as compared with that of the wild-type enzyme.
4. A metA allele which encodes a homoserine transsuccinylase as claimed in claim 1 .
5. A plasmid, wherein it contains a metA allele as claimed in claim 4 together with a promoter.
6. A microorganism strain, wherein it contains a metA allele as claimed in claim 4 .
7. A microorganism strain as claimed in claim 6 , wherein it is a Gram-negative bacterial strain.
8. A method for preparing L-methionine or SAM by culturing a microorganism strain as claimed in claim 6 .