Two uncommon phospholipase D isoenzymes from poppy seedlings (Papaver somniferum L.).
Phospholipase D (PLD) has been detected in seedlings of Papaver somniferum L. cv. Lazúr (Papaveraceae). Purification of the enzyme revealed the existence of two forms of PLD (named as PLD-A and PLD-B). The two enzymes strongly differ in their catalytic properties. The pH optima were found at pH 8.0 for PLD-A and at pH 5.5 for PLD-B. While both enzymes show hydrolytic activity toward phosphatidylcholine (PC) and phosphatidyl-p-nitrophenol (PpNP), PLD-B only was able to catalyze the exchange of choline in PC by glycerol. Both enzymes were activated by Ca(2+) ions with an optimum concentration of 10 mM. In contrast to PLDs from other plants, PLD-B was still more activated by Zn(2+) ions with an optimum concentration of 5 mM. The apparent molecular masses of PLD-A and PLD-B, derived from sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE), were estimated to be 116.4 and 114.1 kDa. N-terminal protein sequencing indicated N-terminal blockage in both cases. The isoelectric points were found to be 8.7 for PLD-A and 6.7 for PLD-B. Both enzymes were shown to be N-linked glycoproteins. This paper is the first report on PLD in poppy and indicates some important differences of the two enzyme forms to other PLDs known so far.
Oblozinsky
Marek
M
Department of Cell and Molecular Biology of Drugs, Faculty of Pharmacy, Comenius University, Kalinciakova 8, SK-83232 Bratislava, Slovak Republic.
Schoeps
Regina
R
Ulbrich-Hofmann
Renate
R
Bezakova
Lydia
L
D002122:Calcium Chloride; D002712:Chlorides; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D007527:Isoenzymes / Q000737:chemistry / Q000302:isolation & purification; D008970:Molecular Weight; D010207:Papaver / Q000201:enzymology*; D010739:Phospholipase D / Q000737:chemistry / Q000302:isolation & purification*; D036226:Seedlings / Q000201:enzymology; D017967:Zinc Compounds
D002712:Chlorides; D007527:Isoenzymes; D017967:Zinc Compounds; C016837:zinc chloride; D010739:Phospholipase D; D002122:Calcium Chloride