The glyoxysomal beta-oxidation system in cucumber seedlings: identification of enzymes required for the degradation of unsaturated fatty acids.
Fat-degrading cotyledons from cucumber seedlings were investigated with respect to the enzymes metabolizing cis-unsaturated fatty acids. Isolated glyoxysomes degrade linoleic acid, the dominating fatty acid in the storage tissue of the seed. Glyoxysomes were shown to be the sole intracellular site of enzymes responsible for the degradation of unsaturated fatty acids. All three auxiliary enzyme activities discussed for the degradation of polyunsaturated fatty acids, 2,4-dienoyl-CoA reductase, enoyl-CoA isomerase, and 3-hydroxyacyl-CoA epimerase were localized within the matrix of glyoxysomes. They were not found in mitochondria. Separation of glyoxysomal matrix proteins on CM-cellulose revealed that epimerase activity was attributable to the multifunctional protein and also to another protein which apparently exhibited no other beta-oxidation activity. Furthermore, on the basis of the high epimerase activity present in glyoxysomes compared to a much lower 2,4-dienoyl-CoA reductase activity, the metabolism of unsaturated fatty acids via delta 2-cis-enoyl-CoA is considered as alternative to the reductase-dependent pathway.
Behrends
W
W
Universität Marburg, Federal Republic of Germany.
Thieringer
R
R
Engeland
K
K
Kunau
W H
WH
Kindl
H
H
D019748:Carbon-Carbon Double Bond Isomerases; D002849:Chromatography, Gas; D064006:Dodecenoyl-CoA Isomerase; D044943:Fatty Acid Desaturases / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D007535:Isomerases / Q000378:metabolism; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000378:metabolism; D008830:Microbodies / Q000201:enzymology*; D044925:Oxidoreductases Acting on CH-CH Group Donors; D010944:Plants / Q000201:enzymology* / Q000648:ultrastructure; D019998:Racemases and Epimerases / Q000378:metabolism
D005231:Fatty Acids, Unsaturated; D008041:Linoleic Acids; D019787:Linoleic Acid; D044943:Fatty Acid Desaturases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C100153:2,4-dienoyl-CoA reductase; D007535:Isomerases; D019998:Racemases and Epimerases; C029601:3-hydroxybutyryl-CoA epimerase; D019748:Carbon-Carbon Double Bond Isomerases; D064006:Dodecenoyl-CoA Isomerase