Studies on the Denaturation and Conformation of Choline Dehydrogenase

The substrate choline was able to improve the pH stability of choline dehydrogenase (CDH). It was found that during the thermal denaturation there were an increase of beta-structure and a decrease of the alpha-helix content. Changes in beta-structure were attributed to beta-turn and 3(10)-helix. The substrate had a protective effect on CDH thermal denaturation. The proportion of 3(10)-helix content of the SDS-denatured protein and that in the presence of substrate was 33% and 31.2% respectively; while, the corresponding proportion of beta-sheet was 29% and 10.6%, respectively. Moreover, when the absorption proportion of alpha-helix, random coil and the side-chain of tyrosine residues were concerned, it was found that the spectral property of the CDH treated by denaturants in the presence of substrate were rather similar to that of the non-denatured enzyme.