The gene encoding a novel L-ribose isomerase (L-RI) from Acinetobacter sp. was cloned into Escherichia coli and nucleotide sequence was determined. The gene corresponded to an open reading frame of 747 bp that codes for a deduced protein of 249 amino acids, which showed no amino acid sequence similarity with any other sugar isomerases. After expression of the gene in E. coli using pUC118 the recombinant L-RI was purified to homogeneity using different chromatographic methods. The overall enzymatic properties of the purified recombinant L-RI were the same as those of the authentic L-RI. To our knowledge, this is the first time report concerning the L-RI gene.