Abstract: The present invention relates to variant aldolase enzymes that are modified so as to produce IHOG, a process for producing an optically active IHOG using the same, and a process for producing an optically active monatin.

Abstract: O-acetylserine, L-cysteine and sulphurous compounds derived therefrom may be produced using a bacterium belonging to the genus Escherichia which harbors a mutant feedback-resistant serine acetyltransferases in which the amino acid sequence corresponding to positions from 89 to 96 in a wild-type serine acetyltransferase is replaced with any one of the amino acid sequences shown in SEQ ID NOS: 4 to 9, and feedback inhibition by L-cysteine in the bacterium is desensitized.

Abstract: The present invention relates to a method for designing and preparing mutant transglutaminases on the basis of the three-dimensional structure of MTG derived from Streptoverticillium mobaraense (MTG), and the mutant MTG thus prepared. The present invention provides a method for modifying MTG on the basis of the three-dimensional structure, and transglutaminase having reactivity on the substrate improved by the method. In the present invention, the binding site of MTG for the substrate is extrapolated based on the three-dimensional structure obtained by X-ray crystal structure analysis of MTG crystals, and the mutant transglutaminases are designed and produced by replacing, inserting or deleting amino acid residues positioned at the substrate-binding site of the transglutaminase.