EFFECT OF LIPASE-DIGESTION ON PHOTOCHEMICAL ACTIVITIES OF ISOLATED CHLOROPLASTS

Abstract

In order to elucidate the role of lipids in photosynthesis, chloroplasts were digested with lipase, and the effect of lipase-digestion on some photochemical activities was studied. The HILL reaction was sensitive to the digestion, but chloroplasts having intact membrane were somewhat resistant to the action of lipase. The inactivation by lipase digestion seems to be due to the destruction of a component necessary for the Hill reaction to proceed. The chloroplasts treated with lipase showed the following activities. (1) Active photooxidation of reduced cytochrome c and menadione. (2) Photooxidation of ascorbate, which was enhanced in the presence of DPIP, and retarded in the absence of the dye. (3) NADP-photoreduction in the presence of the DPIP-ascorbate couple, as the electron donor. These facts suggested that the site attacked with lipase was responsible for the photochemical oxygen evolution. The decrease in the fluorescence intensity of chlorophyll a was also observed during the digestion.