[Glucose isomerase of S. violaceoniger. Fundamental and applied aspects]

XylA gene of Streptomyces violaceoniger (Drocourt et coll. 1988) code for a D-xylose isomerase activity which is used as a D-glucose isomerase activity in large scale. This gene is a part of regulated region involved in xylose utilization (Marcel et coll. 1987). Sequence determination of this region enabled us to characterize xylB gene (Xylulose kinase activity) and xylX gene which is involved in xylA and xylB expression. In order to construct a new strain having a strong and constitutive glucose isomerase activity, a newly isolated strong streptomyces promoter (P1 promoter), has been cloned behind xylA gene. To avoid instability of plasmid and glucose-isomerase activity, the P1-xylA gene of S. violaceoniger has been integrated into the chromosome, using the integrative vector pTS55. The resultant CBS1 strain has four to five fold higher glucose-isomerase activity in absence of xylose compared to that of strain SV1 fully induced by xylose. In addition, specific glucose-isomerase activity of CBS1 strain increases in the secondary growth phase, in contrast to wild type and SV1 strains.