Terminal Oxidation System in Baker's Yeast
IV. Cytochrome b2 and Yeast L-Lactic Dehydrogenase
1962 年 52 巻 2 号 p. 117-124
詳細
1962 年 52 巻 2 号 p. 117-124
1. Sedimention constant, diffusion coefficient and iron content of cytochrome b2 were measured. The sedimentation constant was determined to be 2.2 S, the diffusion coefficient 10.8×10-7cm2. sec.-1, and iron content 0.24 per cent. The molecular weight of cytochrome b2 was calculated as 18, 000 from the physicochemical values, and as 22, 000 from the iron content.
2. Cytochrome b2 had absorption maxima at 275, 359, 411 and 534mμ in its oxidized state and at 422, 528 and 557mμ in its reduced state, the molar extinction coefficient at 557 my was found to be 37.9×103M-1cm.-1. The absorption maxima of the reduced pyridine haemochromogen of cytochrome b2 were at 419, 528 and 557mμ.
3. In neutral solution CO had no effect on the absorption spectrum of reduced cytochrome b2, but in acidic solution, it combined with CO, giving absorption maxima at 419, 543 and 575mμ. Cytochrome b2 appeared to have no affinity for CN- or N3-.
4. In acidic and alkaline solution, the methylene blue- and cytochrome c-reducing activity of yeast L-lactic dehydrogenase were lost more rapidly than the phenazine methosulphate-reducing activity.
From these findings, a possibility was discussed that yeast L-lactic dehydrogenase consists of a dehydrogenase moiety and a haem protein moiety.
The authors would like to express their thanks to Prof. B. Hagihara of this university for technical help in the use of the oxygen electrode and to Mr. K. Fujii (Oriental Yeast Co., Ltd., Osaka) for kindly supplying large quantities of baker's yeast.
