Enzymatic Studies on Purified 5-Lipoxygenase

DeWolf, Walter E.

doi:10.1016/b978-0-12-197800-6.50009-3

Cited by 6 publications

(1 citation statement)

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“…Preferences for the Physical Form of the Substrate and Activation of Potato 5-LOX. The critical importance of knowing the preferences of LOX for the different physical forms of its substrate has recently been stated because this is the only way to correctly analyze the kinetic data (De Wolf, 1991;Ford-Hutchinson et al, 1994) and thus perform correct extrapolations to physiological conditions. The preference of soybean LOX-I for monomeric LA has long been known (Galpin and Allen, 1977), although, rather than being a common case, it is an exception when the pH range at which most LOXs act and the low concentration of monomers at those pH values are taken into consideration.…”

Section: Discussionmentioning

confidence: 99%

Potato (Solanum tuberosum Var. Desiree) Tuber 5-Lipoxygenase Selectivity for the Physicochemical Properties of Linoleic Acid

Bru

García-Carmona

1997

J. Agric. Food Chem.

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The dependence of potato 5-lipoxygenase (LOX) activity on the physicochemical properties of linoleic acid (LA) was studied. pH and β-cyclodextrin (β-CD) were used as tools to investigate the effect of the physicochemical state of LA on LOX kinetic properties in vitro. The LA concentration dependence of LOX activity was best fitted by using the Hill equation. It was found that the decrease of LOX activity at high pH corresponds to a pK a lower than the pK a of LA; thus, such decrease was assigned to some ionizable side chain group of LOX related to the active center. At a fixed LA concentration, the presence of β-CD led to a decrease in the LOX reaction rate, which was due to its effect on K and the Hill constant since V max was not affected. Experiments in the presence of β-CD revealed that LA monomers were also used as substrate, although less efficiently than aggregates. The different activities exhibited against monomers and aggregates is the reason for the observed apparent substrate cooperativity, which can be interpreted as an aggregate-induced enzyme activation. The effect of β-CD on LOX activity could be explained on the basis of the specific interaction between LA and β-CD and the equations derived for such interaction developed in a previous work. Keywords: Potato tuber; 5-lipoxygenase; PUFA; cyclodextrins; fatty acid aggregates; Solanum tuberosum var. Desiree

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Section: Discussionmentioning

confidence: 99%