Literature summary for 1.13.11.B6 extracted from

Gardner, H.W.
Soybean lipoxygenase-1 enzymically forms both (9S)- and (13S)-hydroperoxides from linoleic acid by a pH-dependent mechanism (1989), Biochim. Biophys. Acta, 1001, 274-281.

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Organism

Organism	UniProt	Comment	Textmining
Glycine max	-	-	-

Substrates and Products (Substrate)

Substrates	Comment Substrates	Organism	Products	Comment (Products)	Rev.	Reac.
linoleate + O2	soybean lipoxygenase-1 produces a preponderance of two chiral products from linoleic acid, (9Z,11E,13S)-13-hydroperoxy-9,11-octadecadienoate and (9S,10E,12Z)-9-hydroperoxy-10,12-octadecadienoate. (9Z,11E,13S)-13-hydroperoxy-9,11-octadecadienoate is generated at all pH values, but in the presence of Tween 20, (9S,10E,12Z)-9-hydroperoxy-10,12-octadecadienoate does not form at pH values above 8.5. As the pH decreases below 8.5, the proportion of (9S,10E,12Z)-9-hydroperoxy-10,12-octadecadienoate increases linearly until at pH 6 it constitutes about 25% of the chiral products attributed to enzymic action. Below pH 6, lipoxygenase activity is barely measurable, and the hydroperoxide product arises mainly from autoxidation and possibly non-enzymic oxygenation of the pentadienyl radical formed by the enzyme. The change in percent enzymically formed 9-hydroperoxide between pH 6.0 and 8.5 parallels the pH plot of a sodium linoleate/linoleic acid titration. It is concluded that the (9S)-hydroperoxide is formed only from the nonionized carboxylic acid form of linoleic acid. Methyl esterification of linoleic acid blocks the formation of the (9S,10E,12Z)-9-hydroperoxy-10,12-octadecadienoate by lipoxygenase-1, but not the (13S)-hydroperoxide. Since the hydroperoxydiene moieties of the (9S)- and (13S)-hydroperoxides are spatially identical when the molecules are arranged head to tail in opposite orientations, it is suggested that the carboxylic acid form of the substrate can arrange itself at the active site in either orientation, but the carboxylate anion can be positioned only in one orientation. Active-site model for soybean lipoxygenase-1	Glycine max	(9S,10E,12Z)-9-hydroperoxy-10,12-octadecadienoate + (9Z,11E,13S)-13-hydroperoxy-9,11-octadecadienoate	-	?

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Release 2023.1 (January 2023)