Brandis_1996_Plant.Physiol.Biochem_34_49

Chlorophyllase (Chlase) (EC 3.1.1.14) catalyzes the removal of phytol chain from chlorophyll (Chl), which is one of the initial steps of the natural breakdown of Chl during senescence. Chlase has been assumed to be a component of the thylakoid membranes. We have examined the association of Chlase with specific thylakoid Chl-protein complexes, using a non-denaturing Deriphat PAGE system (green gels). Chl-protein multicomplexes of orange leaves were separated into photosystem I (PSI), its core complex (CCI), oligomeric and monomeric forms of the light-harvesting complex of photosystem II (LHCIIo and LHCIIm), and a free pigment (FP) band. The separated complexes, as well as empty spaces between them, were extracted from the gel, and Chlase activity was determined. Chlase activity was consistently found in proximity to the LHCIIm ; with some activity also present in a colourless zone, close to the front of LHCIIm. Little or no Chlase activity was detected in LHCIIo zone. Chlase activity of yellow orange fruit peel, which apparently does not contain Chl-protein components, also migrated to the same zone as that of young and mature leaves. Incubation of LHCIIo in the presence of detergents increased the LHCIIm but did not release more Chlase activity. In sucrose gradient separations Chlase activity was not confined to Chl-protein complexes and was detectable in other fractions, including the plastid envelope fraction. Critical assessment of the data indicates that the comigration of Chlase activity with LHCIIm may be incidental and does not represent a real association of Chlase with Chl-protein complexes.