Studies on the Spectral Properties of Choline Dehydrogenase

The addition of the substrate didn't show any influence on the intrinsic emission spectra of purified CDH, which had a maximum at 335 nm. On the other hand, the 520 nm fluorescence of CDH increased after the addition of substrate. The secondary structure of solubilized CDH was examined by Fourier-transform infrared spectroscopy. The percentage distribution of its secondary structure assignment had been obtained: 53.4% alpha-helix, 24.5% beta-sheet, 13.9% 3(10)-helix and 0.5% beta-turn. The predominant conformation of CDH was alpha-helix and beta-sheet when there was no substrate. After the addition of substrate, the percentage of 3(10)-helix structure increased to 42%, whereas that of alpha-helix structure decreased to 35%, indicating that the conformation of CDH changed significantly after the binding of substrate of substrate to the enzyme.