Reaction mechanism of 5,8-linoleate diol synthase, 10R-dioxygenase, and 8,11-hydroperoxide isomerase of Aspergillus clavatus.
Biochim Biophys Acta
; 1801(4): 503-7, 2010 Apr.
Article
em En
| MEDLINE
| ID: mdl-20045744
ABSTRACT
Aspergilli express fusion proteins of an animal haem peroxidase domain with fatty acid dioxygenase (DOX) activity ( approximately 600 amino acids) and a functional or non-functional hydroperoxide isomerase/cytochrome P450 domain ( approximately 500 amino acids with EXXR and GPHXCLG motifs). 5,8-Linoleate diol synthases (LDS; ppoA) and 10R-DOX (ppoC) of Aspergillusnidulans and A. fumigatus belong to this group. Our objective was to determine the oxylipins formed from linoleic acid by A. clavatus and their mechanism of biosynthesis. A. clavatus oxidized linoleic acid to (8R)-hydroperoxylinoleic acid (8R-HPODE), (10R)-hydroperoxy-8(E),12(Z)-octadecadienoic acid (10R-HPODE), and to (5S,8R)-dihydroxy- and (8R,11S)-dihydroxylinoleic acids (DiHODE) as major products. This occurred by abstraction of the pro-S hydrogen at C-8 and antarafacial dioxygenation at C-8 or at C-10 with double bond migration. 8R-HPODE was then isomerized to 5S,8R-DiHODE and to 8R,11S-DiHODE by abstraction of the pro-S hydrogens at C-5 and C-11 of 8R-HPODE, respectively, followed by suprafacial oxygenation. The genome of A. clavatus codes for two enzymes, which can be aligned with >65% amino acid identity to 10R-DOX and 5,8-LDS, respectively. The 5,8-LDS homologue likely forms and isomerizes 8R-HPODE to 5S,8R-DiHODE. A third gene (ppoB) codes for a protein which carries a serine residue at the cysteine position of the P450 motif. This Cys to Ser replacement is known to abolish P450 2B4 catalysis and the hydroperoxide isomerase activity of 5,8-LDS, suggesting that ppoB of A. clavatus may not be involved in the biosynthesis of 8R,11S-DiHODE.
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Base de dados:
MEDLINE
Assunto principal:
Oxigenases
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Aspergillus
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Oxirredutases Intramoleculares
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Dioxigenases
Idioma:
En
Ano de publicação:
2010
Tipo de documento:
Article