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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 (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
x * 99500, calculated from sequence Momordica charantia


Organism UniProt Comment Textmining
Momordica charantia B7FDE5

Source Tissue

Source Tissue Comment Organism Textmining
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 Comment Organism
? x * 99500, calculated from sequence Momordica charantia


Synonyms Comment Organism
Momordica charantia

pH Optimum

pH Optimum Minimum pH Optimum Maximum Comment Organism
Momordica charantia