PHYSICAL AND KINETIC EFFECTS ON INTRODUCTION OF VARIOUS LINKER REGIONS IN BETA-GALACTOSIDASE GALACTOSE DEHYDROGENASE FUSION ENZYMES

To examine the role of the connecting region in the artificial bifunct ional enzyme beta-galactosidase/galactose dehydrogenase, linkers of di fferent length were inserted between the catalytic units. The specific activity of the galactose dehydrogenase part of the complex was incre ased when longer linkers (9 and 13 amino acids) were used as connector s, These bifunctional enzymes were predominantly found to comprise hex amers, however, complexes of higher molecular weight were also formed. The sequential reaction was carried out more efficiently when hybrid enzymes with the longer linkers were used as demonstrated both in vitr o by using purified protein preparations as well as in vivo by determi ning the growth rates of recombinant E. coli cells on a minimal medium containing lactose.