PDBsum entry 3cli

Lyase

PDB id: 3cli

Contents

Protein chains

465 a.a. *

Ligands

HEM ×2

GOL

Waters ×647

* Residue conservation analysis

PDB id:

3cli

Name:

Lyase

Title:

Crystal structure of arabidopsis thaliana allene oxide synthase (aos, cytochrome p450 74a, cyp74a) at 1.80 a resolution

Structure:

Allene oxide synthase. Chain: a, b. Synonym: cytochrome p450 74a, chloroplast. Hydroperoxide dehydrase. Engineered: yes

Source:

Arabidopsis thaliana. Mouse-ear cress. Organism_taxid: 3702. Gene: aos, cyp74a. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.80Å R-factor: 0.171 R-free: 0.198

Authors:

D.-S.Lee,P.Nioche,C.S.Raman

Key ref:

D.S.Lee et al. (2008). Structural insights into the evolutionary paths of oxylipin biosynthetic enzymes. Nature, 455, 363-368. PubMed id: 18716621 DOI: 10.1038/nature07307

Date:

19-Mar-08 Release date: 19-Aug-08

Protein chains

Q96242  (CP74A_ARATH) -  Allene oxide synthase, chloroplastic from Arabidopsis thaliana

Seq: 518 a.a.

Struc: 465 a.a.

Enzyme reactions

• Enzyme class: E.C.4.2.1.92 - hydroperoxide dehydratase.
• Reaction: (13S)-hydroperoxy-(9Z,11E,15Z)-octadecatrienoate = (9Z,13S,15Z)-12,13- epoxyoctadeca-9,11,15-trienoate + H2O
• Cofactor: Heme-thiolate

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

Key reference

DOI no: 10.1038/nature07307

Nature 455:363-368 (2008)

PubMed id: 18716621

Structural insights into the evolutionary paths of oxylipin biosynthetic enzymes.

D.S.Lee, P.Nioche, M.Hamberg, C.S.Raman.

ABSTRACT

The oxylipin pathway generates not only prostaglandin-like jasmonates but also green leaf volatiles (GLVs), which confer characteristic aromas to fruits and vegetables. Although allene oxide synthase (AOS) and hydroperoxide lyase are atypical cytochrome P450 family members involved in the synthesis of jasmonates and GLVs, respectively, it is unknown how these enzymes rearrange their hydroperoxide substrates into different products. Here we present the crystal structures of Arabidopsis thaliana AOS, free and in complex with substrate or intermediate analogues. The structures reveal an unusual active site poised to control the reactivity of an epoxyallylic radical and its cation by means of interactions with an aromatic pi-system. Replacing the amino acid involved in these steps by a non-polar residue markedly reduces AOS activity and, unexpectedly, is both necessary and sufficient for converting AOS into a GLV biosynthetic enzyme. Furthermore, by combining our structural data with bioinformatic and biochemical analyses, we have discovered previously unknown hydroperoxide lyase in plant growth-promoting rhizobacteria, AOS in coral, and epoxyalcohol synthase in amphioxus. These results indicate that oxylipin biosynthetic genes were present in the last common ancestor of plants and animals, but were subsequently lost in all metazoan lineages except Placozoa, Cnidaria and Cephalochordata.

Selected figure(s)

Figure 1.
Figure 1: Reactions catalysed by the CYP74 enzyme family. In higher plants, C[18] fatty acids (linoleic and linolenic acids) are oxygenated at either position 9 or 13 by lipoxygenases to yield hydroperoxides. Subsequently, these are converted by allene oxide synthase (AOS, also known as CYP74A), hydroperoxide lyase (HPL, also known as CYP74B) and divinyl ether synthase (DES, also known as CYP74D) to allene oxide (an essential intermediate in jasmonate biosynthesis), green leaf volatiles (aldehydes) and divinyl ethers, respectively. For clarity, only 13-hydroperoxide-derived metabolites are shown. 12,13(S)-allene oxide, 12,13S-epoxy-9Z,11,15Z-octadecatrienoic acid; 13(S)-HPOT, 13S-hydroperoxyoctadecatrienoic acid; -ketol is the hydrolytic product of the highly unstable allene oxide; hemiacetal, hydroxyhexenyloxydodecadienoic acid.

Figure 4.
Figure 4: Proposed reaction paths for AOS and HPL on the basis of the current structural and enzymological studies^14, ^15, ^16, ^17, ^21. The intermediate epoxyallylic radical formed in step 4 can either undergo one electron oxidation followed by proton loss (AOS) or oxygen rebound (HPL). The structure of the peroxide substrate is abbreviated to highlight the region undergoing chemical transformation. For clarity, the Fe–S bond between the haem iron and Cys 471 is only shown in step 1. It remains intact throughout the catalytic cycle. Hydrogen bonds are illustrated with blue dashed lines.

The above figures are reprinted by permission from Macmillan Publishers Ltd: Nature (2008, 455, 363-368) copyright 2008.

Figures were selected by an automated process.