Partial marker cassette mutagenesis of xylose isomerase

摘要

Constructions and methods for mutagenesis of nucleic acids involve chemical mutagenesis of a cassette comprising a structural gene linked to a non-functional restorable fragment of a marker gene. Mutants are detected by screening for the presence of the reconstituted marker among the ligation products of the cassette to a vector containing the non-functional restorable remainder of the marker gene. Xylose isomerase mutants, characterized by a change from glu (GAG) to lys (AAG) at amino acid position 262 in the xylA protein of E. coli were obtained by partial marker cassette mutagenesis. These mutants enzymes exhibited twice the rate of isomerization of glucose to fructose exhibited by the wild type.