Identification, separation, and characterization of acyl-coenzyme A dehydrogenases involved in mitochondrial beta-oxidation in higher plants

The existence in higher plants of an additional beta-oxidation system in mitochondria, besides the well-characterized peroxisomal system, is often considered controversial. Unequivocal demonstration of beta-oxidation activity in mitochondria should rely on identification of the enzymes specific to m...

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Bibliographic Details
Published inPlant physiology Vol. 119; no. 4
Main Authors Bode, K, Hooks, M.A, Couee, I
Format Publication
LanguageEnglish
Published 1999
Subjects
ACYL-COA DEHYDROGENASE
ACYL-COA OXIDASE
ASSAYS
BIOCHEMICAL PATHWAYS
CATALASE
COMPLEMENTARY DNA
ENZYME ACTIVITY
HELIANTHUS ANNUUS
HYDRO-LYASES
MITOCHONDRIA
NUCLEOTIDE SEQUENCES
OXIDATION
OXIDOREDUCTASES
PEROXISOMES
ROOT TIPS
SEED GERMINATION
SEEDS
SUBSTRATES
ZEA MAYS
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Summary:The existence in higher plants of an additional beta-oxidation system in mitochondria, besides the well-characterized peroxisomal system, is often considered controversial. Unequivocal demonstration of beta-oxidation activity in mitochondria should rely on identification of the enzymes specific to mitochondrial beta-oxidation. Acylcoenzyme A dehydrogenase (ACAD) (EC 1.3.99.2,3) activity was detected in purified mitochondria from maize (Zea mays L.) root tips and from embryonic axes of early-germinating sunflower (Helianthus annuus L.) seeds, using as the enzyme assay the reduction of 2,6-dichlorophenolindophenol, with phenazine methosulfate as the intermediate electron carrier. Subcellular fractionation showed that this ACAD activity was associated with mitochondria fractions. Comparison of ACAD activity in mitochondria and acylcoenzyme A oxidase activity in peroxisomes showed differences of substrate specificities. Embryonic axes of sunflower seeds were used as starting material for the purification of ACADs. Two distinct ACADs, with medium-chain and long-chain substrate specificities, respectively, were separated by their chromatographic behavior, which was similar to that of mammalian ACADs. The characterization of these ACADs is discussed in relation to the identification of expressed sequenced tags corresponding to ACADs in cDNA sequence analysis projects and with the potential roles of mitochondrial beta-oxidation in higher plants.
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