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The induction by xylose and repression by glucose of xylose isomerase(XI) were investigated to elucidate the regulation for production of XI in Escherichia coli. Regulation for expression of xylA gene which codes XI is under control of xylR, which is a regulatory gene for xylose catabolism. When xylR gene was resided in chromosome, the inductions of XI by the addition of 0.4%. xylose were increased to 1.9 and 1.7-fold in case of locating on multicopy(pEX202/DH77) and low copy plasmid(pEX102/DH77), respectively, as compared with that of xylA gene which was resided in chromosome(JM109). xylR gene product derived from xylR gene on chromosome might react to xylA gene on the plasmid as same as xylA gene on chromosome. In JM109 and xylA transformant; pEX202/DH77 and pEX102/DH77, the inductions of XI were completely repressed by the addition of 0.2% glucose and these catabolite repressions were derepressed by the addition of 1 mM cAMP. In comparison with the addition of 0.4% xylose only for the induction XI was inductively produced 1.7 to 2-fold with the addition of xylose plus 1 mM cAMP in DM minimal media. pEX13/TP2010, xylA transformant of the deficient mutant(xyl, cya ; TP2010) of XI and cAMP production, did not induce XI by the addition of xylose only but induced in case of simultaneous addition of xylose and CAMP. These resets show that cAMP and xylose are the indispensable effectors for the induction and derepression of XI in E. coli.
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