Scientia Sinica

88 SCIENTIA SINICA Vol. V

10

105

Optical density

25 300. 3520 34O 360 380 400 420 440 460

240 260 280 300 320 340 360 380 400 420 440 460 Wavelength, mp

Fig. 10. Absorption spectrum of the isolated prosthetic group. The insert shows the absorption spectrum in the violet region in greater detail.

by hydrogen sulphide. This is essentially the method of Warburg and Christian’) for the purification of flavin-adenine dinucleotide. .

The prosthetic group was thus obtained as a yellow aqueous solution, showing greenish yellow fluorescence, and has an absorption spectrum as shown in Fig. 10, with maxima at 270, 340, and 450 my. It is bleached by reduction with Na-dithionite and the reduced solution is no longer fluorescent. The fluorescent intensity of the prosthetic group varies with pH and shows a maximum at pH 3. This property is similar to that reported in the literature for flavin-adenine dinucleotide" *!, It has some flavin-adenine dinucleotide activity in the D-amino acid oxidase test.

Discussion

From the electrophoretic pattern it is seen that the purified preparation of succinic dehydrogenase obtained by our procedure is practically homogeneous except for a small trace of protein with higher mobility which could not be