Evidence for the existence of isozymes of glucose isomerase from Streptomyces phaeochromogenes.

Glucose isomerase from Streptomyces phaeochromogenes was purified from a commercial preparation, Swetase, by DEAE-cellulose, Bio-Gel A-0.5 m, and hydroxyapatite column chromatographies. It was found to be 2 fractions; F-A, not adsorbed on hydroxyapatite and F-B, adsorbed on hydroxyapatite. They were homogeneous in ordinary and SDS-PAGE and had similarities in some enzymatic and physico-chemical properties. The differences, however, were found in the N-terminal amino acid, which was only serine for F-A while it was serine and alanine for F-B, and also in their peptide mapping patterns of digests with trypsin, Achromobacter protease I, and cyanogen bromide. The results suggest that glucose isomerase from S. phaeochromogenes was composed of the two kinds of isozymes and that each of isozymes was a tetramer constituted of non-identical subunits.