Molecular Characterization of a Heteromeric ATP-Citrate Lyase That Generates Cytosolic Acetyl-Coenzyme A in Arabidopsis,

Abstract

Acetyl-coenzyme A (CoA) is used in the cytosol of plant cells for the synthesis of a diverse set of phytochemicals including waxes, isoprenoids, stilbenes, and flavonoids. The source of cytosolic acetyl-CoA is unclear. We identified two Arabidopsis cDNAs that encode proteins similar to the amino and carboxy portions of human ATP-citrate lyase (ACL). Coexpression of these cDNAs in yeast (Saccharomyces cerevisiae) confers ACL activity, indicating that both the Arabidopsis genes are required for ACL activity. Arabidopsis ACL is a heteromeric enzyme composed of two distinct subunits, ACLA (45 kD) and ACLB (65 kD). The holoprotein has a molecular mass of 500 kD, which corresponds to a heterooctomer with an A 4 B 4 configuration. ACL activity and the ACLA and ACLB polypeptides are located in the cytosol, consistent with the lack of targeting peptides in the ACLA and ACLB sequences. In the Arabidopsis genome, three genes encode for the ACLA subunit (ACLA-1, At1g10670; ACLA-2, At1g60810; and ACLA-3, At1g09430), and two genes encode the ACLB subunit (ACLB-1, At3g06650 and ACLB-2, At5g49460). The ACLA and ACLB mRNAs accumulate in coordinated spatial and temporal patterns during plant development. This complex accumulation pattern is consistent with the predicted physiological needs for cytosolic acetyl-CoA, and is closely coordinated with the accumulation pattern of cytosolic acetyl-CoA carboxylase, an enzyme using cytosolic acetyl-CoA as a substrate. Taken together, these results indicate that ACL, encoded by the ACLA and ACLB genes of Arabidopsis, generates cytosolic acetyl-CoA. The heteromeric organization of this enzyme is common to green plants (including Chlorophyceae, Marchantimorpha, Bryopsida, Pinaceae, monocotyledons, and eudicots), species of fungi, Glaucophytes, Chlamydomonas, and prokaryotes. In contrast, all known animal ACL enzymes have a homomeric structure, indicating that a evolutionary fusion of the ACLA and ACLB genes probably occurred early in the evolutionary history of this kingdom.Acetyl-coenzyme A (CoA) is an intermediate metabolite that is juxtaposed between catabolic and anabolic processes. As the entry point for the tricarboxylic acid (TCA) cycle, acetyl-CoA can be considered the gateway in the oxidation of carbon derived from the catabolism of fatty acids, certain amino acids (e.g. Leu, Ile, Lys, and Trp), and carbohydrates. Furthermore, acetyl-CoA is the intermediate precursor for the biosynthesis of a wide variety of phytochemicals. Because membranes are impermeable to CoA derivatives, it can be inferred that acetyl-CoA is generated in at least four distinct metabolic pools representing the four subcellular compartments where acetyl-CoA metabolism occurs: plastids, mitochondria, peroxisomes, and the cytosol (Fig. 1). Therefore, plants should have distinct acetyl-CoA-generating systems in mitochondria (for the TCA cycle), in plastids (for de novo fatty acid biosynthesis), in peroxisomes (the product of ␤-oxidation of fatty acids), and in the cytosol (for the biosynthesis of isoprenoids, flavo...

Erucic acid rapeseed: 1. Prospects of improvements

“…Fatty acid elongation is a cytosolic process, and cytosolic ATP-citrate lyase (ACL) generates the required acetyl-CoA precursor. The temporal distribution of ATP-citrate lyase (ACL) activity in developing seeds of rapeseed closely paralleled both that of acetyl-CoA carboxylase (ACCase) in the cytosol and the overall rate of lipid biosynthesis (Fatland et al, 2002). In the cytosol, acetyl-CoA can be carboxylated by ACCase to form malonyl-CoA and hence is converted to long chain fatty acids.…”

“…Cytosolic acetyl-CoA is metabolized via one of three mechanisms: carboxylation, condensation, or acetylation. In the cytosol, acetyl-CoA can be carboxylated by acetyl-CoA carboxylase to form malonyl-CoA (Fatland et al, 2002). Cytosolic malonyl-CoA is required for the biosynthesis of long chain fatty acids like erucic acid (22:1).…”

Association of genetic variations in the ACLY gene with growth traits in Chinese beef cattle

“…ATP citrate lyase is a member of the acyl-CoA synthetase (ADP-forming) superfamily (Sánchez et al, 2000), and consists of ACLA and ACLB subunits (Fatland et al, 2002). In mammals, ACLY is a homotetramer, containing an ATP-grasp domain (N-terminal region), a CoA binding domain, a CoA-ligase, and citrate synthetase (C-terminal region) (Morita et al, 2014).…”

Multi-scale genetic network inference based on time series gene expression profiles

“…The microarray type was an Affymetrix GeneChip. The data consisted of two replicates; each with eleven time points (0, 0.5,1,4,8, 8.5, 9, 12, 14,16, 20 hours), and changing from light (from 0 to 8 hours) to dark (from 8 to 20 hours) (Fatland, Ke et al 2002;Foster, Ling et al 2004). Only ACLA-1 seedlings exhibiting features characteristic of the antisense phenotype were used.…”

“…Figure 4-1 shows an example of highly coregulated gene expression profiles in the diurnal biological process of the model plant Arabidopsis (a member of the mustard family, widely used as a model organism in plant biology) (Fatland, Ke et al 2002;Foster, Ling et al 2004). Clustering is widely used to find these coregulated genes Spell man, Sherlock et al 1998;Iyer, Eisen et al 1999; …”