HETEROLOGOUS EXPRESSION, PURIFICATION, AND PROPERTIES OF DIOL DEHYDRATASE, AN ADENOSYLCOBALAMIN-DEPENDENT ENZYME OF KLEBSIELLA-OXYTOCA

Recombinant adenosylcobalamin-dependent diol dehydratase of Klebsiella oxytoca overexpressed in Escherichia coli was purified to homogeneity . The enzyme has a low solubility and was extracted from the crude mem brane fraction with 1% Brij 35 in a high recovery. Subsequent chromato graphy on DEAE-cellulose resulted in 4.9-fold purification of the enzy me in an overall yield of 65%. The enzyme thus obtained showed specifi c activity comparable to that of the wild-type enzyme of K. oxytoca. T he apparent molecular weight determined by nondenaturing gel electroph oresis on a gradient gel was 220,000. The enzyme consists of equimolar amounts of the three subunits with apparent M-r of 60,000 (alpha), 30 ,000 (beta), and 19,000 (gamma). Therefore, the subunit structure of t he enzyme is most likely alpha(2) beta(2) gamma(2). The recombinant en zyme was also separated into components F and S upon DEAE-cellulose ch romatography in the absence of substrate. Components F and S were iden tified as the beta subunit and alpha(2) gamma(2) complex, respectively . Apparent K-m for adenosylcobalamin, 1,2-propanediol, glycerol, and 1 ,2-ethanediol were 0.83 mu M, 0.08 mM, 0.73 mM, and 0.56 mM, respectiv ely. The three genes encoding the subunits of diol dehydratase were ov erexpressed individually or in various combinations in Escherichia col i. The alpha and gamma subunits mutually required each other for corre ct folding forming the soluble, active alpha(2) gamma(2) complex (comp onent S). Expression of the beta subunit in a soluble, active form (co mponent F) was promoted by coexpression with both the alpha and gamma subunits, probably by coexistence with component S. These lines of evi dence indicate that each subunit mutually affects the folding of the o thers in this heterooligomer enzyme. (C) 1997 Academic Press.