Incorporation of newly synthesized fatty acids into cytosolic glycerolipids in pea leaves occurs via acyl editing

Philip D Bates; John B Ohlrogge; Mike Pollard

doi:10.1074/jbc.M705447200

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Incorporation of newly synthesized fatty acids into cytosolic glycerolipids in pea leaves occurs via acyl editing

Journal article

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Incorporation of newly synthesized fatty acids into cytosolic glycerolipids in pea leaves occurs via acyl editing

Philip D Bates, John B Ohlrogge and Mike Pollard

The Journal of biological chemistry, Vol.282(43), pp.31206-31216

10/26/2007

DOI: https://doi.org/10.1074/jbc.M705447200

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https://hdl.handle.net/2376/100442

PMID: 17728247

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Abstract

Carbon Dioxide - metabolism

Acetates - metabolism

Lipid Metabolism

Glycerol - metabolism

Plant Leaves - metabolism

Models, Biological

Cytosol - metabolism

Carbon Radioisotopes - metabolism

Kinetics

Fatty Acids - metabolism

Peas - metabolism

Acylation

Fatty Acids - biosynthesis

Seedlings - metabolism

In expanding pea leaves, over 95% of fatty acids (FA) synthesized in the plastid are exported for assembly of eukaryotic glycerolipids. It is often assumed that the major products of plastid FA synthesis (18:1 and 16:0) are first incorporated into 16:0/18:1 and 18:1/18:1 molecular species of phosphatidic acid (PA), which are then converted to phosphatidylcholine (PC), the major eukaryotic phospholipid and site of acyl desaturation. However, by labeling lipids of pea leaves with [(14)C]acetate, [(14)C]glycerol, and [(14)C]carbon dioxide, we demonstrate that acyl editing is an integral component of eukaryotic glycerolipid synthesis. First, no precursor-product relationship between PA and PC [(14)C]acyl chains was observed at very early time points. Second, analysis of PC molecular species at these early time points showed that >90% of newly synthesized [(14)C]18:1 and [(14)C]16:0 acyl groups were incorporated into PC alongside a previously synthesized unlabeled acyl group (18:2, 18:3, or 16:0). And third, [(14)C]glycerol labeling produced PC molecular species highly enriched with 18:2, 18:3, and 16:0 FA, and not 18:1, the major product of plastid fatty acid synthesis. In conclusion, we propose that most newly synthesized acyl groups are not immediately utilized for PA synthesis, but instead are incorporated directly into PC through an acyl editing mechanism that operates at both sn-1 and sn-2 positions. Additionally, the acyl groups removed by acyl editing are largely used for the net synthesis of PC through glycerol 3-phosphate acylation.

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Title: Incorporation of newly synthesized fatty acids into cytosolic glycerolipids in pea leaves occurs via acyl editing
Creators: Philip D Bates - Department of Biochemistry, Michigan State University, East Lansing, Michigan 48824, USA
John B Ohlrogge
Mike Pollard
Publication Details: The Journal of biological chemistry, Vol.282(43), pp.31206-31216
Academic Unit: Biological Chemistry, Institute of
Publisher: United States
Identifiers: 99900546638101842
Language: English
Resource Type: Journal article