Inhibition of the plastidial phosphatidylcholine synthesis by silver, copper, lead and mercury induced by formation of mercaptides with the lyso-PC acyltransferase.
Plastids greatly rely on the import of extraplastidial precursors for the synthesis of their own lipids, and several studies have shown that a lyso-PC acyltransferase located in the envelope may be involved in the import process. Because the presence of heavy metals in soil or in nutrient solutions induces changes in the lipid composition of plastid membranes (and therefore greatly reduces the photosynthetic capability of plants), we analysed the effect of several metal salts on plastidial lyso-PC acyltransferase activity. Among the 12 heavy metals studied, silver, copper, mercury and lead inhibited this activity. Metal bound to the enzyme was not - or only very slightly - released from the protein except when thiol-reducing agents (and not imidazole) were added. The results strongly suggest that the inhibitory effect is due to a formation of mercaptide between metal and cysteine(s). The relationship between the inhibition of the plastidial lyso-PC acyltransferase activity and the in vivo effects of metal salts on the plastid membranes is discussed.
Akermoun
Malika
M
UMR 5544/ESTBB, CNRS-Université Victor Segalen, Bordeaux II, Bordeaux, France.
Testet
Eric
E
Cassagne
Claude
C
Bessoule
Jean-Jacques
JJ
D008243:1-Acylglycerophosphocholine O-Acyltransferase / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D003300:Copper / Q000378:metabolism / Q000494:pharmacology; D003545:Cysteine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D007854:Lead / Q000378:metabolism / Q000494:pharmacology; D008628:Mercury / Q000378:metabolism / Q000494:pharmacology; D019216:Metals, Heavy / Q000378:metabolism / Q000494:pharmacology*; D010713:Phosphatidylcholines / Q000096:biosynthesis*; D018087:Plastids / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D011485:Protein Binding; D012834:Silver / Q000378:metabolism / Q000494:pharmacology
D004791:Enzyme Inhibitors; D019216:Metals, Heavy; D010713:Phosphatidylcholines; D007854:Lead; D012834:Silver; D003300:Copper; D008243:1-Acylglycerophosphocholine O-Acyltransferase; D008628:Mercury; D003545:Cysteine