Guanidinium- and temperature-induced conformational changes in glucose dehydrogenase.
The conformational changes in glucose dehydrogenase are studied as a function of temperature and guanidinium chloride (GdmCl) concentration. The data were analyzed assuming a two-conformer model which gave similar results using either circular dichroism or enzyme activity. The free energy of denaturation was 0.94 kcal/mol from specific activity and 1.64 kcal/mol from circular dichroism measurements. The mid-point of the denaturation curve was 0.65 or 0.63 M GdmCl, as determined by specific activity or circular dichroism, respectively. The transition temperature, 6.4 degrees C, is close to that of a microsomal membrane phase change, a result that is consistent with the fact that glucose dehydrogenase contains lipid materials when isolated with a non-ionic detergent such as Triton X-114. As the temperature increased, the amount of beta-pleated sheet increased, and the alpha-helical content decreased, suggested that glucose dehydrogenase contains a stable core of beta-pleated sheet.
D000818:Animals; D002237:Carbohydrate Dehydrogenases / Q000378:metabolism*; D002942:Circular Dichroism; D005948:Glucose Dehydrogenases / Q000378:metabolism*; D019791:Guanidine; D006146:Guanidines; D008099:Liver / Q000201:enzymology; D011487:Protein Conformation; D013552:Swine; D013696:Temperature; D013816:Thermodynamics
D006146:Guanidines; D002237:Carbohydrate Dehydrogenases; D005948:Glucose Dehydrogenases; D019791:Guanidine