Overexpression and characterization of a recombinant l-ribose isomerase from Actinotalea fermentans ATCC 43279.

A putative l-ribose isomerase (EC 5.3.1.B3, l-RI) gene of Actinotalea fermentans ATCC 43279 was chemically synthesized, subcloned into pET-21b vector, and then overexpressed in Escherichia coli. After 0.5mM IPTG induction at 20°C for 20h, the recombinant l-RI was highly expressed with up to 50% of the total proteins. About 70% of the expressed l-RI appeared in the cell-free extract as a soluble form, and a high yield of active l-RI, 23,800U/L or 952U/g of wet cells, was achieved. The purified recombinant l-RI demonstrated its optimal activity at 45°C and pH 8 (in tricine-NaOH buffer). Metal ions are not required for l-RI activity, but Hg