Galactolipid Synthesis in Isolated Pea Chloroplasts
UDPgal transferase (UDPGT) activity has been localized in the outer chloroplast envelope membrane (OEM) of pea (18: 3 plant) (1) and in the inner chloroplast envelope membrane (IEM) of spinach (16: 3 plant) (2). This seems logical in the context of current ideas concerning the sources of diglyceride for the galactosylation reaction (3). However, analysis of the molecular species of MGDG extracted from thylakoid membranes isolated from sequential segments of young oat seedling shoots (4) shows that although the 18: 3/18: 3 molecular specie predominates at all developmental stages, there are significant proportions of 18: 1/16: 0 and 18: 3/16: 0 molecular species in thylakoids from the younger plastids. This suggested to us that UDPGT may be present in both membranes each galactosylating the diglycerides available to it. The following experiments have been carried out with plastids isolated from expanding leaves of pea with the aim of corroborating previous research with pea chloroplasts.
KeywordsThylakoid Membrane Molecular Species Envelope Membrane Plant Lipid Cular Species
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