Chlorophyll synthetase is latent in well preserved prolamellar bodies of etiolated wheat

Membrane fractions containing intact etioplasts, etioplast inner membranes, prolamellar bodies or prothylakoids from wheat ( Triticum aestivum L. cv. Walde) were assayed for chlorophyll synthetase activity. Calculated on a protein basis, the etioplast inner membrane fraction showed a higher activity than the intact etioplasts. The activity was higher in the prolamellar body fraction than in the prothylakoid fraction. However, when the fractions were incubated in isolation medium with 50% (w/w) sucrose and 0.3 m M NADPH, chlorophyll synthetase activity could not be detected in the prolamellar body fraction, while the prothylakoid fraction maintained a high activity. The spectral shift to a shorter wavelength of the newly formed endogenous chlorophyllide was very rapid in the prothylakoid fraction but slow in the prolamellar body fraction. The relation between the spectral shift of chlorophyllide and the esterification activity in the fractions is discussed. Even exogenous short-wavelength chlorophyllide could not be esterified in well preserved prolamellar bodies. This indicates that chlorophyll synthetase is present in an inactive state in the prolamellar body structure. A large-scale method for the synthesis of geranylgeranylpyrophosphate, one of the substrates of the chlorophyll synthetase reaction, is also presented.