Limits...
A lipoxygenase from red alga Pyropia haitanensis, a unique enzyme catalyzing the free radical reactions of polyunsaturated fatty acids with triple ethylenic bonds.

Zhu Z, Qian F, Yang R, Chen J, Luo Q, Chen H, Yan X - PLoS ONE (2015)

Bottom Line: It was found that at least triple ethylenic bonds are required for PhLOX2 to function as a LOX, and the resulting hydroxy products should be originated from the PhLOX2 mediated reduction of mono-hydroperoxides, in which the hydrogen abstraction occurs on the carbon atom between the second and third double bond.Most of the di-hydroperoxides observed seem to be missing their mono-position precursors.The substrate and position flexibility, as well as the function versatility of PhLOXs represent the ancient enzymatic pathway for organisms to control intracellular oxylipins.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Applied Marine Biotechnology, Ningbo University, Ningbo, Zhejiang, 315211, China.

ABSTRACT
Lipoxygenases (LOXs) are key enzymes to regulate the production of hormones and defensive metabolites in plants, animals and algae. In this research, a full length LOX gene has been cloned and expressed from the red alga Pyropia haitanensis (Bangiales, Rhodophyta) gametophyte (PhLOX2). Subsequent phylogenetic analysis showed that such LOX enzymes are separated at the early stage of evolution, establishing an independent branch. The LOX activity was investigated at the optimal pH of 8.0. It appears that PhLOX2 is a multifunctional enzyme featuring both lipoxygenase and hydroperoxidase activities. Additionally, PhLOX2 exhibits remarkable substrate and position flexibility, and it can catalyze an array of chemical reactions involving various polyunsaturated fatty acids, ranging from C18 to C22. As a matter of fact, mono-hydroperoxy, di-hydroperoxy and hydroxyl products have been obtained from such transformations, and eicosapentaenoic acid seem to be the most preferred substrate. It was found that at least triple ethylenic bonds are required for PhLOX2 to function as a LOX, and the resulting hydroxy products should be originated from the PhLOX2 mediated reduction of mono-hydroperoxides, in which the hydrogen abstraction occurs on the carbon atom between the second and third double bond. Most of the di-hydroperoxides observed seem to be missing their mono-position precursors. The substrate and position flexibility, as well as the function versatility of PhLOXs represent the ancient enzymatic pathway for organisms to control intracellular oxylipins.

No MeSH data available.


Related in: MedlinePlus

Amino acid sequence alignment.The sequence of PhLOX2 was aligned with the PhLOX protein (AFQ59981) from P. haitanensis and the PpLOX protein from P. purpurea (AAA61791) using ClustalX program, and the results were displayed with GeneDoc. Numbers in the right-hand margin refer to amino acid residues. Identical and similar residues are shown on the background as black and gray, respectively. The LOX protein includes SRPBCC (single underline) domain and LOX (double underline) domain. The five essential conserved residues (His-585, His-590, His-774, Asn-778 and Ile-899) in the active site, which are involved in the binding of iron, have been marked with asterisks.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4319731&req=5

pone.0117351.g001: Amino acid sequence alignment.The sequence of PhLOX2 was aligned with the PhLOX protein (AFQ59981) from P. haitanensis and the PpLOX protein from P. purpurea (AAA61791) using ClustalX program, and the results were displayed with GeneDoc. Numbers in the right-hand margin refer to amino acid residues. Identical and similar residues are shown on the background as black and gray, respectively. The LOX protein includes SRPBCC (single underline) domain and LOX (double underline) domain. The five essential conserved residues (His-585, His-590, His-774, Asn-778 and Ile-899) in the active site, which are involved in the binding of iron, have been marked with asterisks.

Mentions: The entire sequence of PhLOX2 showed the highest identity to PpLOX from P. purpurea (AAA61791) and PhLOX from P. haitanensis (AFQ59981), whose sequence identity to PhLOX2 was 57% and 50%, respectively. The alignment of amino acid sequence for PhLOX2, PhLOX and PpLOX is shown in Fig. 1. Specifically, a low sequence similarity was found within the N-terminal portion of the protein, which was directed to the SRPBCC (START/RHOalphaC/PITP/Bet v1/CoxG/CalC) superfamily. It has a deep hydrophobic ligand-binding pocket and can bind diverse ligands. Included in this superfamily are the steroidogenic acute regulatory protein (StAR)-related lipid transfer (START) domains of mammalian STARD1-STARD15, and the C-terminal catalytic domains of the alpha oxygenase subunit of Rieske-type non-heme iron aromatic ring-hydroxylating oxygenases (RHOs_alpha_C), as well as the SRPBCC domains of phosphatidylinositol transfer proteins (PITPs). While all the other known LOXs have an N-terminal PLAT domain, which is used to direct the protein to the membrane [12]. The LOX from P. haitanisis lacks this part of the protein, but its C-terminal domain consisting primarily of α-helices and containing the catalytic sites of the enzyme exhibits similarity to other LOXs. Especially the central histidine-rich region around His-585, His-590, His-774, Asn-778 and Ile-899, which are involved in iron binding within the active site, are highly conserved (Fig. 1, marked by asterisks).


A lipoxygenase from red alga Pyropia haitanensis, a unique enzyme catalyzing the free radical reactions of polyunsaturated fatty acids with triple ethylenic bonds.

Zhu Z, Qian F, Yang R, Chen J, Luo Q, Chen H, Yan X - PLoS ONE (2015)

Amino acid sequence alignment.The sequence of PhLOX2 was aligned with the PhLOX protein (AFQ59981) from P. haitanensis and the PpLOX protein from P. purpurea (AAA61791) using ClustalX program, and the results were displayed with GeneDoc. Numbers in the right-hand margin refer to amino acid residues. Identical and similar residues are shown on the background as black and gray, respectively. The LOX protein includes SRPBCC (single underline) domain and LOX (double underline) domain. The five essential conserved residues (His-585, His-590, His-774, Asn-778 and Ile-899) in the active site, which are involved in the binding of iron, have been marked with asterisks.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4319731&req=5

pone.0117351.g001: Amino acid sequence alignment.The sequence of PhLOX2 was aligned with the PhLOX protein (AFQ59981) from P. haitanensis and the PpLOX protein from P. purpurea (AAA61791) using ClustalX program, and the results were displayed with GeneDoc. Numbers in the right-hand margin refer to amino acid residues. Identical and similar residues are shown on the background as black and gray, respectively. The LOX protein includes SRPBCC (single underline) domain and LOX (double underline) domain. The five essential conserved residues (His-585, His-590, His-774, Asn-778 and Ile-899) in the active site, which are involved in the binding of iron, have been marked with asterisks.
Mentions: The entire sequence of PhLOX2 showed the highest identity to PpLOX from P. purpurea (AAA61791) and PhLOX from P. haitanensis (AFQ59981), whose sequence identity to PhLOX2 was 57% and 50%, respectively. The alignment of amino acid sequence for PhLOX2, PhLOX and PpLOX is shown in Fig. 1. Specifically, a low sequence similarity was found within the N-terminal portion of the protein, which was directed to the SRPBCC (START/RHOalphaC/PITP/Bet v1/CoxG/CalC) superfamily. It has a deep hydrophobic ligand-binding pocket and can bind diverse ligands. Included in this superfamily are the steroidogenic acute regulatory protein (StAR)-related lipid transfer (START) domains of mammalian STARD1-STARD15, and the C-terminal catalytic domains of the alpha oxygenase subunit of Rieske-type non-heme iron aromatic ring-hydroxylating oxygenases (RHOs_alpha_C), as well as the SRPBCC domains of phosphatidylinositol transfer proteins (PITPs). While all the other known LOXs have an N-terminal PLAT domain, which is used to direct the protein to the membrane [12]. The LOX from P. haitanisis lacks this part of the protein, but its C-terminal domain consisting primarily of α-helices and containing the catalytic sites of the enzyme exhibits similarity to other LOXs. Especially the central histidine-rich region around His-585, His-590, His-774, Asn-778 and Ile-899, which are involved in iron binding within the active site, are highly conserved (Fig. 1, marked by asterisks).

Bottom Line: It was found that at least triple ethylenic bonds are required for PhLOX2 to function as a LOX, and the resulting hydroxy products should be originated from the PhLOX2 mediated reduction of mono-hydroperoxides, in which the hydrogen abstraction occurs on the carbon atom between the second and third double bond.Most of the di-hydroperoxides observed seem to be missing their mono-position precursors.The substrate and position flexibility, as well as the function versatility of PhLOXs represent the ancient enzymatic pathway for organisms to control intracellular oxylipins.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Applied Marine Biotechnology, Ningbo University, Ningbo, Zhejiang, 315211, China.

ABSTRACT
Lipoxygenases (LOXs) are key enzymes to regulate the production of hormones and defensive metabolites in plants, animals and algae. In this research, a full length LOX gene has been cloned and expressed from the red alga Pyropia haitanensis (Bangiales, Rhodophyta) gametophyte (PhLOX2). Subsequent phylogenetic analysis showed that such LOX enzymes are separated at the early stage of evolution, establishing an independent branch. The LOX activity was investigated at the optimal pH of 8.0. It appears that PhLOX2 is a multifunctional enzyme featuring both lipoxygenase and hydroperoxidase activities. Additionally, PhLOX2 exhibits remarkable substrate and position flexibility, and it can catalyze an array of chemical reactions involving various polyunsaturated fatty acids, ranging from C18 to C22. As a matter of fact, mono-hydroperoxy, di-hydroperoxy and hydroxyl products have been obtained from such transformations, and eicosapentaenoic acid seem to be the most preferred substrate. It was found that at least triple ethylenic bonds are required for PhLOX2 to function as a LOX, and the resulting hydroxy products should be originated from the PhLOX2 mediated reduction of mono-hydroperoxides, in which the hydrogen abstraction occurs on the carbon atom between the second and third double bond. Most of the di-hydroperoxides observed seem to be missing their mono-position precursors. The substrate and position flexibility, as well as the function versatility of PhLOXs represent the ancient enzymatic pathway for organisms to control intracellular oxylipins.

No MeSH data available.


Related in: MedlinePlus