植物のウイルス感染機作 (III)

Abstract

Properties of the phosphatases in green leaves and the change of their activities in the course of virus infection were investigated. The pH optimum of this enzyme lies between 5.8 to 6.0 using β-sodium glycerophosphate as substrate. Adding MgCl2 as an activator, alkaline (optimum pH, 9.4) pyrophosphatase was demonstrated in the green juices, while only a little alkaline glycerophosphatase. The acid glycerophosphatase activity was reduced by half for 5 minutes' exposure to 60°C and inhibited by NaF, but not influenced by Mg ion. The fractionation of the juices of the mosaic leaves revealed that the plastid fraction has no its activity, nevertheless that the fraction of the resultant precipitates by adding ammonium sulphate until 0.6 saturated to the supernatant after centrifuging the homogenized juice at 1, 000 G has about 90 per cent activity.The detached leaves of tobacco, tomato, turnip, and spinach inoculated with tobacco mosaic virus or turnip mosaic virus were placed in water or in nutrient solution and their phosphatase activities were estimated at the different times from inoculation. Sometimes the plants grown in pots in greenhouse were also tested. From these experiments it appears that the acid phosphatases have the tendencies to decrease in the later stage of infection. Despite of that some of the data concerning the increased activities of phosphatases, especially those of alkaline pyrophosphatase, were obtained in an initial stage of the infection, it is thought desirable to conduct a more detailed experiment on this problem in future. In some case, however, it happens that the inoculated leaves, especially those of tobacco plants, do not show during virus infection any detectable difference in the activity compared with the uninoculated leaves. On the basis of these findings, the metabolic process of the virus-infected leaves was discussed.