STUDIES ON TYROSINASE
III. The effect of the addition of various salts on the potato tyrosinase
1938 年 28 巻 3 号 p. 383-403
詳細
1938 年 28 巻 3 号 p. 383-403
The potato tyrosinase was purified successively by precipita-tion with alcohol, by adsorption with aluminium hydroxide suspen-sion Cr and electrodialysis and by use of these enzyme prepara-tions the effect of the addition of various salts on the tyrosinase action was examined.
1. Tyrosinase shows a wide range of optimum pH between pH 7 and 9. No appreciable difference in the optimum pH is observed in the experiments with three enzyme preparations of different purities. At reactions more alkaline than pH 11 or more acid than pH 4 tyrosinase rapidly loses its activity.
2. The optimum temperature for the tyrosinase action lies at 35-40°.
3. KCN, AgNO3, HgCl2, MnCl2, K3Fe(CN)6 and KMnO4, inhibit the action of tyrosinase, whereas FeSO4, K4Fe(CN)6 and FeSO4(NH4)2SO4 bring about its activation. No essential dif-ference is noted between the experiments with alumina prepara-tions and electrodialysant.
4. The inhibiting action of KCN takes place only at the alkaline reaction, due to the liberation of HCN from the acid reac-tion mixtures by shaking in the Warburg's vessel.
5. The acceleration of tyrosinase by FeSO4, K4Fe(CN)6 and FeSO4(NH4)2SO4 occurs mainly at the acid reactions.
6. MnCl2 depresses the tyrosinase action only at a definite concentration. At higher or lower concentrations than this the inhibition occurs to a less extent. At acid reactions a larger amount of salt is necessary to bring about the maximum inhibition. At pH 7.38 the addition of 1/4400 mol MnCl2 always causes the maximum inhibition, irrespective of the amount of enzyme added or the purity of the enzyme preparations employed.
In the conclusion I wish to express my thanks to Assist. Prof. T. Uchino for his guidance throughout the course of this investi-gation.
The expense of this research was defrayed by the Foundation for the Promotion of Scientific and Industrial Research in Japan.
