The phosphatidic acid phosphatase of the chloroplast envelope is located on the inner envelope membrane

Abstract

The envelope from spinach chloroplasts contains an alkaline phosphatidic acid phosphatase which was found to be located on the inner envelope membrane. The diacylglycerol formed by this enzyme from endogenous phosphatidic acid is then used as a substrate for galactolipid synthesis on the inner envelope membrane.

Molecular aspects of plastid envelope biochemistry

“…These values are very high, especially for the outer envelope membrane which contains much more lipid than any other plant cell membrane. Therefore, envelope membranes have a rather low density: 1.08 and 1.12-1.13 g/cm3 for the outer and the inner envelope membranes, respectively [8], which allow their clean separation by density gradient centrifugation [8,91. The glycerolipid composition of chloroplast and nongreen plastid membranes is given in Table 1.…”

“…This enzyme is present in envelope membrane from chloroplasts [37] and non-green plastids [45]. In spinach chloroplasts, both the outer and the inner envelope membranes contain this acyltransferase [8], but in pea chloroplasts only the inner membrane does [46]. Since lysophosphatidic acid used for this reaction is esterified at the sn-1 position, the enzyme will direct Fatty acids [almost exclusively palmitic acid (16:O)l to the available sn-2 position [38, 391. Therefore, the two plastid acyltransferases have distinct specificities and selectivities for acylation of sn-glycerol-3-phosphate (Fig.…”

Transit sequence‐dependent binding of the chloroplast precursor protein ferredoxin to lipid vesicles and its implications for membrane stability

“…The extended bilayers of LUVETs serve as a model system for the lipid domains of the chloroplast outer envelope membranes. These membranes have a high lipid-toprotein ratio [10] and the lipids are accessible for proteins because externally added lipid-specific antibodies can interact with chloroplasts [11]. We have chosen to use the precursor 0014-5793195l$9.50 © 1995 Federation of European Biochemical Societies.…”

Role of phosphatidic acid in plant galactolipid synthesis

“…A typical chloroplast envelope PA phosphatase has been described in the past [34]. This enzyme is tightly associated with the inner envelope membrane [35,36]. In contrast to most PA phosphatases, it shows an alkaline optimum pH, a severe inhibition by Mg 2þ suggesting a link with photosynthetic activity and a strong feedback inhibition by DAG suggesting that PA hydrolysis and galactolipid synthesis are coupled in the membrane.…”