Thylakoid-associated «Chlorophyll Oxidase»: Distinction from Lipoxygenase

Abstract

Barley chloroplasts contain a latent chlorophyll-bleaching activity. It is closely associated with the thylakoid, and depends on the presence of free fatty acids such as linolenic acid. Chlorophyll-bleaching is strictly dependent on oxygen. The principle responsible for the linolenate-dependent bleaching effect is tentatively termed «chlorophyll oxidase».

The effects of various inhibitors, particularly chelators of Cu and Fe on «chlorophyll oxidase» resemble the effects on the bleaching of chlorophyll by soybean lipoxygenase in the presence of linolenic acid. However, «chlorophyll oxidase» differs clearly from lipoxygenase in that pigment-bleaching is not associated with the production of linolenate hydroperoxide. Moreover, «chlorophyll oxidase» is active in the presence of oleic- and even stearic acid and thus is distinct from lipoxygenase which requires fatty acids containing a 1,4 pentadiene unit.