An ancient relative of cyclooxygenase in cyanobacteria is a linoleate 10S-dioxygenase that works in tandem with a catalase-related protein with specific 10S-hydroperoxide lyase activity [Enzymology]

March 21st, 2014 by Brash, A. R., Niraula, N. P., Boeglin, W. E., Mashhadi, Z.

In the course of exploring the scope of catalase-related hemoproteins′ reactivity towards fatty acid hydroperoxides, we detected a novel candidate in the cyanobacterium Nostoc punctiforme PCC 73102. The immediate neighboring upstream gene, annotated as ″cyclooxygenase-2″, appeared to be a potential fatty acid heme dioxygenase. We cloned both genes and expressed the cDNAs in E. coli, confirming their hemoprotein character. Oxygen electrode recordings demonstrated a rapid (>100 turnovers/s) reaction of the heme dioxygenase with oleic, and linoleic acids. HPLC including chiral column analysis, UV, and GC-MS of the oxygenated products identified a novel 10S-dioxygenase activity. The catalase-related hemoprotein reacted rapidly and specifically with linoleate 10S-hydroperoxide (> 2,500 turnovers/s) with a hydroperoxide lyase activity specific for the 10S-hydroperoxy enantiomer. The products were identified by NMR as (8E) 10-oxo-decenoic acid and the C8 fragments, 1-octen-3-ol and 2Z-octen-1-ol in ~ 3:1 ratio. Chiral HPLC analysis established strict enzymatic control in formation of the 3R alcohol configuration (99% ee) and contrasted with racemic 1-octen-3-ol formed in reaction of linoleate 10S-hydroperoxide with hematin or ferrous ions. The Nostoc linoleate 10S-dioxygenase, the sequence of which contains the signature catalytic sequence of cyclooxygenases and fungal linoleate dioxygenases (YRWH) appears to be a heme dioxygenase ancestor. The novel activity of the lyase expands the known reactions of catalase-related proteins and functions in Nostoc in specific transformation of the 10S-hydroperoxylinoleate.
  • Posted in Journal of Biological Chemistry, Publications
  • Comments Off on An ancient relative of cyclooxygenase in cyanobacteria is a linoleate 10S-dioxygenase that works in tandem with a catalase-related protein with specific 10S-hydroperoxide lyase activity [Enzymology]