The reaction mechanism of allene oxide synthase: Interplay of theoretical QM/MM calculations and experimental investigations

• Published in: Archives of biochemistry and biophysics 2011-03, Vol.507 (1), p.14-25
• Main Authors: Cho, Kyung-Bin, Lai, Wenzhen, Hamberg, Mats, Raman, C.S., Shaik, Sason
• Format: Article
• Language: English
• Subjects: Aldehyde-Lyases - metabolism; Alkadienes - metabolism; Allene oxide synthase; Arabidopsis; Arabidopsis - chemistry; Arabidopsis - enzymology; Arabidopsis - genetics; Compound II; CYP74; Cytochrome P-450 Enzyme System - chemistry; Cytochrome P-450 Enzyme System - genetics; Cytochrome P-450 Enzyme System - metabolism; Epoxy Compounds - metabolism; Hydroperoxide lyase; Intramolecular Oxidoreductases - chemistry; Intramolecular Oxidoreductases - genetics; Intramolecular Oxidoreductases - metabolism; linoleic acid; Linoleic Acids - chemistry; Linoleic Acids - metabolism; Models, Molecular; Mutation; Oryza - chemistry; Oryza - enzymology; Oryza - genetics; Oxides - metabolism; P450; QM/MM; Quantum Theory; rice
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/j.abb.2010.07.016

► Combined theory and experiment decipher the mechanism of AOS and its link to HPL. ► Experiment shows that wild-type AOS produces both AOS and HPL products in a ratio of about 80:15. ► Theory deciphers the AOS pathway with 13( S)-hydroperoxy linolenic and linoleic acid as substrate. ► In silico F137L mutation results reproduce three out of four experimentally available cases. A combined theoretical and experimental study highlights the reaction mechanism of allene oxide synthase (AOS) and its possible link to hydroperoxide lyase (HPL) pathway. A previously published study (Lee et al., Nature 455 (2008) 363) has shown that the F137 residue is of central importance in differentiating between the AOS and HPL pathways after initial identical steps. In the experimental part of this study, we show that wild-type AOS from Arabidopsis or rice in fact produces both AOS and HPL products in a ratio of about 80:15, something that was found only in trace amounts before. Theoretical calculations successfully map the whole AOS pathway with 13( S)-hydroperoxy linolenic and linoleic acid as substrates. Subsequent calculations investigated the effects of in silico F137L mutation at the suggested diverging point of the two pathways. The results show that QM/MM calculations can reasonably reproduce three out of four experimentally available cases, and confirm that the pathways are energetically very close to each other, thus making a switch from one path to other plausible under different circumstances.