Any feedback?
Please rate this page
(literature.php)
(0/150)

BRENDA support

Literature summary for 1.13.11.B6 extracted from

  • Hornung, E.; Kunze, S.; Liavonchanka, A.; Zimmermann, G.; Khn, D.; Fritsche, K.; Renz, A.; Khn, H.; Feussner, I.
    Identification of an amino acid determinant of pH regiospecificity in a seed lipoxygenase from Momordica charantia (2008), Phytochemistry, 69, 2774-2780.
    View publication on PubMed

Cloned(Commentary)

Cloned (Comment) Organism
expressed as a His-tagged fusion protein in Escherichia coli Momordica charantia

Protein Variants

Protein Variants Comment Organism
Q599F the wild-type enzyme is a linoleate 13-LOX above pH 7.5, below this value it functions as a linoleate 9-LOX. The mutant loses its 13-LOX activity at higher pH-values. At pH-values above 7.5 a rather unspecific product pattern (1:1 ratio of 13-hydroperoxy-(10E,12Z)-octadecadienoate and 9-hydroperoxy-(10E,12Z)-octadecadienoate) is observed with the mutant enzyme. The unspecific oxygenation reaction is also indicated by the R/S-ratio (4:6) of the major reaction products Momordica charantia
Q599H the mutation converts the enzyme to a linoleate 13-LOX lacking any pH sensitivity. The pH optimum remains unaffected, and the major product isomers are in the S-configuration Momordica charantia

Molecular Weight [Da]

Molecular Weight [Da] Molecular Weight Maximum [Da] Comment Organism
99500
-
x * 99500, calculated from sequence Momordica charantia

Organism

Organism UniProt Comment Textmining
Momordica charantia B7FDE5
-
-

Source Tissue

Source Tissue Comment Organism Textmining
seed
-
Momordica charantia
-

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
linoleate + O2 according to their positional specificity of linoleic acid oxygenation plant LOX can be classified into linoleate 9-lipoxygenases and linoleate 13-lipoxygenases. A critical valine is detected at the active site of 9-LOX. In contrast, more bulky phenylalanine or histidine residues are found at this position in 13-LOX. Cloning of LOX-isoform from Momordica charantia and multiple amino acid alignments indicate the existence of a glutamine (Gln599) at the position where 13-LOX usually carry histidine or phenylalanine residues. Analyzing the pH-dependence of the positional specificity of linoleic acid oxygenation it is observed that at pH-values higher than 7.5 this enzyme constitutes a linoleate 13-lipoxygenase whereas at lower pH, (9S)-hydroperoxy-(10E,12Z)-octadecadienoate is the major reaction product. The structural basis for this variable reaction specificity is explored by site directed mutagenesis studies. Site-directed mutagenesis of Gln599 to His (Gln599His) converts the enzyme to a pure 13-lipoxygenase. The reaction specificity of certain LOX-isoforms is not an absolute enzyme property but may be impacted by reaction conditions such as pH of the reaction mixture Momordica charantia (10E,12Z)-9-hydroperoxy-10,12-octadecadienoate + (9Z,11E)-13-hydroperoxy-9,11-octadecadienoate variable positional specificity of linoleic acid oxygenation depending on the pH of the reaction mixture. Below pH 7.5, (10E,12Z)-9-hydroperoxy-10,12-octadecadienoate is the major reaction product whereas at higher pH (9Z,11E)-13-hydroperoxy-9,11-octadecadienoate is dominant. (9Z,11E)-13-hydroperoxy-9,11-octadecadienoate is preferentially formed as S enantiomer (85%) and the S/R-ratio does hardly vary over the entire pH-range. In contrast, the enantiomers composition of (10E,12Z)-9-hydroperoxy-10,12-octadecadienoate is pH-dependent. Below pH 7.5 a strong preponderance of the S enantiomer is observed. At higher pH-values the relative share of (9R,10E,12Z)-9-hydroperoxy-10,12-octadecadienoate becomes increasingly abundant reaching a 1:1 ratio at pH 9 ?

Subunits

Subunits Comment Organism
? x * 99500, calculated from sequence Momordica charantia

Synonyms

Synonyms Comment Organism
MoLOX1
-
Momordica charantia

pH Optimum

pH Optimum Minimum pH Optimum Maximum Comment Organism
8
-
-
Momordica charantia