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Stereochemistry of oxidized fatty acids generated during catalytic oxygenation of lauric acid and unsaturated analogs by plant microsomes
Author(s) -
J P Salaün,
D Weissbart,
C Helvig,
F Durst,
P Pflieger,
H Bosch,
C Mioskowski
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)80499-7
Subject(s) - chemistry , lauric acid , stereochemistry , hydroxylation , enantiomer , amino acid , medicinal chemistry , fatty acid , biochemistry , enzyme
The capacity of microsomes from aminopyrine‐induced Jerusalem artichoke ( Helianthus tuberosus L.) to oxidize saturated and unsaturated fatty acids has been investigated using lauric acid and a series of unsaturated lauric acid analogs (7‐, 8‐, 9‐ and 10‐dodecenoic acids) as radiolabeled substrates. In the presence of NADH, lauric acid was mono‐hydroxylated principally at carbon 9. Steric analysis of this product showed a low enantiomeric excess of 28%. Mono‐hydroxylated and mono‐epoxidated reaction products were formed from the unsaturated analogs. The epoxidation/hydroxylation ratio was related to the position of the double bond in the aliphatic chain. The oxidation of 7‐dodecenoic acid (7‐DDNA) and 10‐DDNA produced mainly 9‐hydroxy‐7‐DDNA and 9‐hydroxy‐10‐DDNA plus minor amounts of 7,8‐epoxy‐ or 10,11‐epoxylauric acid, respectively. In contrast, 8‐ and 9‐DDNAs yielded essentially 8,9‐epoxy‐ and 9,10‐epoxylauric acids and smaller amounts of 10‐hydroxy‐9‐DDNA and 8‐hydroxy‐9‐DDNA, respectively. The optical purity and the absolute configuration of the major metabolites were investigated. Epoxidation of Z 8‐DDNA and Z 9‐DDNA occurs with high enantiomeric excesses. When the double bond was in the Z configuration, (8 S ,9 R )/(8 R ,9 S ) 8,9‐epoxylauric acid (93/7) or (9 R ,10 S )/(9 S ,10 R ) 9,10‐epoxylauric acid (89/11) were produced. In contrast, when the double bond was in the E configuration, steric analysis showed an enantiomeric ratio of 52/48 for E 8,9‐epoxide and of 59/41 for E 9,10‐epoxide, Z 7‐DDNA led to the formation of 98% of the 9( S )‐hydroxy‐ Z 7‐DDNA enantiomer, while 9‐hydroxy‐ Z 10‐DDNA derived from Z 10‐DDNA was 35% ( R ) and 65% ( S ).