ABSTRACT
In this chapter, the authors deal with examples of efficient production, analysis of structure-function relationships, and the engineering of starch-processing enzymes by recombinant DNA technology. A comparison of the amino acid sequence of glucoamylases from several fungi and yeasts showed five highly conserved regions. Glucoamylase genes were expressed mostly in yeasts or fungi; no efficient production in bacteria has been reported. Substitutions of Glu-357, Asp-424, and Asp-328 of neopullulanase-corresponding to the catalytic residues of Glu-230, Asp-297, and Asp-206, respectively, of Taka-amylase A-with other amino acids completely inactivated the enzyme. Because a higher temperature gives a higher fructose content, thermostable xylose isomerase should be useful for production of high-fructose corn syrup with a higher fructose content. Although many of the starch-processing enzymes were found many years ago, and their efficient production systems have already been established, production by recombinant bacteria is advantageous for newly found enzymes or for enzymes.
