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The Fatty Acid 8,11‐Diol Synthase of Aspergillus fumigatus is Inhibited by Imidazole Derivatives and Unrelated to PpoB
Author(s) -
Jernerén Fredrik,
Oliw Ernst H.
Publication year - 2012
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/s11745-012-3673-2
Subject(s) - chemistry , aspergillus fumigatus , biosynthesis , atp synthase , stereochemistry , diol , fatty acid synthase , cytochrome p450 , biochemistry , enzyme , polyketide synthase , organic chemistry , biology , polyketide , microbiology and biotechnology
(8 R )‐Hydroperoxy‐(9 Z ,12 Z )‐octadecadienoic acid (8‐HPODE) is formed by aspergilli as an intermediate in biosynthesis of oxylipins with effects on sporulation. 8‐HPODE is transformed by separate diol synthases to (5 S ,8 R )‐dihydroxy‐ and (8 R ,11 S )‐dihydroxy‐(9 Z ,12 Z )‐octadecadienoic acids (5,8‐ and 8,11‐DiHODE). The former is formed by the cytochrome P450 (P450) domain of 5,8‐linoleate diol synthase (5,8‐LDS or PpoA). Our aim was to characterize the 8,11‐diol synthase of Aspergillus fumigatus , which is prominent in many strains. The 8,11‐diol synthase was soluble and had a larger molecular size (>100 kDa) than most P450. Miconazole, ketoconazole, and 1‐benzylimidazole, classical inhibitors of P450, reduced the biosynthesis of 8,11‐DiHODE from 8‐HPODE (apparent IC 50 values ~0.8, ~5, and ~0.6 μM, respectively), but did not inhibit the biosynthesis of 5,8‐DiHODE. Analysis of hydroperoxides of regioisomeric C 18 and C 20 fatty acids showed that the 8,11‐diol synthase was specific for certain hydroperoxides with R configuration. The suprafacial hydrogen abstraction and oxygen insertion at C‐11 of 8‐HPODE was associated with a small deuterium kinetic isotope effect ( H k cat / D k cat ~1.5), consistent with P450‐catalyzed oxidation. The genome of A. fumigatus contains over 70 P450 sequences. The reaction mechanism, size, and solubility of 8,11‐diol synthase pointed to PpoB, a homologue of 5,8‐LDS, as a possible candidate of this activity. Gene deletion of ppoB of A. fumigatus strains AF:∆ku80 and J272 did not inhibit biosynthesis of 8,11‐DiHODE and recombinant PpoB appeared to lack diol synthase activity. We conclude that 8,11‐DiHODE is formed from 8‐HPODE by a soluble and substrate‐specific 8,11‐diol synthase with catalytic characteristics of class III P450.