Purification and characterisation of glucose (xylose) isomerase from Chainia sp. (NCL 82-5-1)

Glucose (xylose) isomerase is an important enzyme in high fructose syrup industry. The enzyme generally occurs intracellularly and is specific for both glucose and xylose. A rare actinomycete Chainia sp. (NCL 82-5-1) produces extracellular specific glucose and xylose isomerases and an intracellular glucose (xylose) isomerase. The intracellular enzyme is isolated by cell autolysis and purified by preparative polyacrylamide gel electrophoresis. Its properties are studied and compared with those of extracellular specific xylose isomerase. The intracellular enzyme has a molecular weight of 1,58,000 daltons with four equal subunits of 40,700 daltons. The N-terminal amino acid sequence analysis shows Arg at the N-terminal. Diethylpyrocarbonate inhibited the enzyme and the inhibition kinetics study shows the presence of at least 2 essential His residues. The amino acid analysis shows the absence of Cys and a high proportion of hydrophobic and acidic amino acids.