title: Studies on the combined action of amylases and glucose isomerase on starch and its hydrolyzate. Part I. Production, extraction, purification and kinetic behavior of glucose isomerase.
abstract: Glucose isomerase was produced from Streptomyces phaeochromogenes by aerobic fermentation at 28 degrees C for 24 hrs. The crude enzyme was obtained by disintegrating the harvested cells. It was found that ammonium sulphate at a saturation of 0.3-0.5 gave the maximum enzyme recovery (88.8%) from the crude extract, while acetone gave 66.2% at a concentration of 3/1 (V/V). On this basis the crude enzyme extract was purified following several steps as concentration, dialysis, precipitation with (NH4)2 SO4, then passing through column of Amberlite CG-50, and the eluate was treated with acetone to precipitate the enzyme. The kinetics behavior was studied and it was found that: optimum D-glucose concentration was 0.8 M, Km was 0.25 M, optimum pH was 7.0 and temperature was 70 degrees C. Magnesium at concentration of 0.07 M gave the maximum activity and its Km was 0.024 M. Antagonistic effects of Na+, Ca++ and Fe+++ in presence of 0.07 M of Mg++ were studied. Km and Vmax at different levels of Mg++ concentration were determined and no change in Km value was observed, while Vmax was affected. These findings indicate that the Mg++ combined with enzyme independently of the substrate.
mesh_terms: D019747:Aldose-Ketose Isomerases; D002238:Carbohydrate Epimerases / Q000302:isolation & purification* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D013302:Streptomyces / Q000201:enzymology*; D013696:Temperature
chemical_list: D002238:Carbohydrate Epimerases; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase; D008274:Magnesium