The invention concerns a homoserine transsuccinylase having at least one mutation compared to a wild-type homoserine transsuccinylase and reduced sensitivity towards a L-methionine or SAM, compared to the wild-type enzyme. The latter comprises an amino acid sequence including a partial AspGlyXaaXaaXaaThrGlyAlaPro sequence between position 90 and position 115 and a partial TyrGlnXaaThrPro sequence between position 285 and position 310, position 1 of the amino acid sequence corresponding to the initial methionine. The invention is characterized in that the mutation is a substitution of the aspartate in the partial AspGlyXaaXaaXaaThrGlyAlaPro sequence, or a substitution of the tyrosine in the partial TyrGlnXaaThrPro sequence.