Acyl-CoA

About: Acyl-CoA is a research topic. Over the lifetime, 527 publications have been published within this topic receiving 25134 citations. The topic is also known as: Acyl Coenzyme A.

Gene isolation and characterization of two acyl CoA oxidases from soybean with broad substrate specificities and enhanced expression in the growing seedling axis.

Abstract: The first committed step in the β-oxidation of fatty acids is catalyzed by the enzyme acyl-CoA oxidase (ACOX), which oxidizes a fatty acyl-CoA to a 2-trans-enoyl-CoA. To understand the role of β-oxidation during seedling growth in soybean, two ACOX cDNAs were isolated by screening a seedling library with a DNA fragment obtained by RT-PCR by using degenerate oligonucleotides. The two cDNAs (ACX1;1 and ACX1;2) are 86% identical to each other at the nucleotide and the amino acid level. Their deduced amino acid sequences share significant homology with known acyl-CoA oxidases, including the conserved CGGHGY motif, a putative flavin mononucleotide binding site. In both sequences, the last three amino acids, ARL, represent a putative peroxisome targeting signal. The mRNA and protein of both cDNAs accumulated in all seedling tissues, with relatively stronger expression in the growing seedling axis and hypocotyl, and weaker expression in the cotyledon. Immunolocalization studies indicated that the two proteins were localized in the phloem cells of hypocotyl tissue. The two cDNAs were expressed in Escherichia coli and shown to possess acyl-CoA oxidase activity. With fatty acyl-CoA substrates of varying chain lengths, it was demonstrated that both ACX1;1 and ACX1;2 have broad substrate specificities (C8–C18). The stronger expression of ACX1;1 and ACX1;2 in the axis and hypocotyl tissue, the weaker expression in the oil-rich cotyledon tissue, and the broad substrate specificities suggest that the two acyl-CoA oxidases might play a general house-keeping role during soybean seedling growth, such as the turnover of membrane lipids.

Long chain fatty acyl-CoA modulation of H2O2 release at mitochondrial complex I

Abstract: Complex I is responsible for most of the mitochondrial H2O2 release, low during the oxidation of the NAD linked substrates and high during succinate oxidation, via reverse electron flow. This H2O2 production appear physiological since it occurs at submillimolar concentrations of succinate also in the presence of NAD substrates in heart (present work) and rat brain mitochondria (Zoccarato et al., Biochem J, 406:125–129, 2007). Long chain fatty acyl-CoAs, but not fatty acids, act as strong inhibitors of succinate dependent H2O2 release. The inhibitory effect of acyl-CoAs is independent of their oxidation, being relieved by carnitine and unaffected or potentiated by malonyl-CoA. The inhibition appears to depend on the unbound form since the acyl-CoA effect decreases at BSA concentrations higher than 2 mg/ml; it is not dependent on ΔpH or Δp and could depend on the inhibition of reverse electron transfer at complex I, since palmitoyl-CoA inhibits the succinate dependent NAD(P) or acetoacetate reduction.

The type 2 acyl-CoA:diacylglycerol acyltransferase family of the oleaginous microalga Lobosphaera incisa.

Abstract: Oleaginous microalgae are promising sources of energy-rich triacylglycerols (TAGs) for direct use for food, feed and industrial applications. Lobosphaera incisa is a fresh water unicellular alga, which in response to nutrient stress accumulates a high amount of TAGs with a high proportion of arachidonic acid (ARA). The final committed step of de novo TAG biosynthesis is catalyzed by acyl-CoA:diacylglycerol acyltransferases (DGATs), which add a fatty acid (FA) to the final sn-3 position of diacylglycerol (DAG). Genome analysis revealed the presence of five putative DGAT isoforms in L. incisa, including one DGAT of type 1, three DGATs of type 2 and a single isoform of a type 3 DGAT. For LiDGAT1, LiDGAT2.1, LiDGAT2.2 and LiDGAT2.3 enzyme activity was confirmed by expressing them in the TAG-deficient yeast strain H1246. Feeding experiments of yeast transformants with fatty acids suggest a broad substrate specificity spectrum for LiDGAT1. A significant TAG production in response to exogenous ARA was found for LiDGAT2.2. Cellular localization of the four type 1 and type 2 DGATs expressed in yeast revealed that they all localize to distinct ER domains. A prominent association of LiDGAT1 with ER domains in close proximity to forming lipid droplets (LDs) was also observed. The data revealed a distinct molecular, functional and cellular nature of type 1 and type 2 DGATs from L. incisa, with LiDGAT1 being a major contributor to the TAG pool. LiDGATs of type 2 might be in turn involved in the incorporation of unusual fatty acids into TAG and thus regulate the composition of TAG. This report provides a valuable resource for the further research of microalgae DGATs oriented towards production of fresh-water strains with higher oil content of valuable composition, not only for oil industry but also for human and animal nutrition.