Localization of Lipolytic Acyl Hydrolase in Chloroplast of Stored Spinach Leaves

Abstract

The localization of lipolytic acyl hydrolase (LAH) in chloroplasts was studied and the change in LAH activity determined in relation to the advance of senescence in spinach leaves stored at 25°C.
Chloroplast fractions were prepared by differential centrifugation and sucrose density gradient centrifugation. From the distribution of chlorophyll and marker enzyme activity, it was found that the LAH was contained in broken as well as intact chloroplasts, suggesting that it may be localized in the chloroplast thylakoids.
The LAH activity of spinach chloroplasts increased after 3 days of storage coinciding with the beginning of leaf yellowing, then decreased with the advance of yellowing.
It is inferred from these results that the chloroplast LAH together with lipoxygenase, degrades the chloroplast lipids with the fatty acid hydroperoxides formed being involved in chlorophyll degradation.