Substrate specificity in phospholipid transformations by plant phospholipase D isoenzymes

Area of Science:

• Biochemistry
• Plant Molecular Biology

Background:

• Phospholipase D (PLD) enzymes are crucial for phospholipid metabolism in plants.
• Multiple PLD isoenzymes exist in plants, but their functional distinctions remain largely uncharacterized.

Purpose of the Study:

• To compare the substrate specificities and transphosphatidylation activities of PLD isoenzymes from white cabbage and opium poppy.
• To elucidate the functional differences between plant PLD isoforms.

Main Methods:

• Recombinant production of two PLD isoenzymes from white cabbage (Brassica oleracea var. capitata) and two from opium poppy (Papaver somniferum L.) in Escherichia coli.
• Assessing hydrolysis of various phospholipids and transphosphatidylation of phosphatidylcholine with different acceptor alcohols in a biphasic buffer-diethyl ether system.

Main Results:

• Highly homologous PLD isoenzymes hydrolyzed phosphatidylcholine, -glycerol, -ethanolamine, and -inositol, with varying rates. Phosphatidylserine hydrolysis was observed with one exception.
• Significant differences in head group exchange rates during transphosphatidylation were noted, with a consistent preference for acceptor alcohols (ethanolamine > glycerol >> l-serine).
• Stereoselectivity was observed for l- and d-serine in PLD activity.

Conclusions:

• Plant PLD isoenzymes exhibit distinct hydrolytic and transphosphatidylation specificities.
• These functional differences suggest specialized physiological roles for different PLD isoforms in plants.