Physicochemical Characterization of Glucose Isomerase fromStreptomyces griseofuscus, S-41

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Abstract
Some physicochemical properties of purified glucose isomerase from Streptomyces griseofuscus, S-41 were examined. The extinction coefficient and isoelectric point (pI) were determined to be 11.4 and 4.0, respectively. The values for sedimentation coefficient , partial specific volume (ῡ) diffusion coefficient (D20w)and intrinsic viscosity ([η])were 8.50 S, 0.73 cm3/g, 4.6 x 107 cm2/sec and 3.7ml/g, respectively. The molecular weight was estimated to be 180,000 by the sedimentation equilibrium method and 185,000 by the gel electrophoretical method. The enzyme was found to contain four cobalt ions per molecule in atomic absorption spectrophotometrical analysis. The CD spectrum in the far ultraviolet region showed a minimum at 280 nm and a maximum at 198 nm. Mean residue ellipticity ([θ ])at 220 nm was estimated to be –11,200 deg • cm2/d mol. The computed values for the contents of the secondary structure were as follows: α-helix, 40%; β-form, 36%; and random coil, 24%. The enzyme showed a visible CD spectrum having a negative peaks at 530 nm and 430 nm. This suggested the formation of a coordinated metal compound, Co-amino acid complex. The molecular dimension of the enzyme was examined by measuring the hydrodynamic parameters. The frictional ratio (a/b) was 5.0 for prolate ellipsoid and 0.2 for oblate ellipsoid. Stokes' radius was calculated to be 47 Å for a hydrated hypothetical sphere.