Kinetics of thermal inactivation of pea seed lipoxygenases and the effect of additives on their thermostability

Mature pea seeds contain two major lipoxygenases (LOX) isoenzymes designated LOX-2 and LOX-3. The thermal inactivation of crude pea LOX and the recombinant LOX (rLOX) were studied. Heat-inactivation plots for crude extracts of pea LOX were linear from which thermodynamic activation parameters, ΔH #,...

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Published inFood chemistry Vol. 65; no. 3; pp. 323 - 329
Main Authors Busto, M.D., Owusu Apenten, R.K., Robinson, D.S., Wu, Z., Casey, R., Hughes, R.K.
Format Journal Article
LanguageEnglish
Published Oxford Elsevier Ltd 01.05.1999
Elsevier
Subjects
Biological and medical sciences
Food industries
Fruit and vegetable industries
Fundamental and applied biological sciences. Psychology
Grain legume
Extracts
Stabilizer agent
Enzyme
Isozyme
Oxidoreductases
Recombinant protein
Lipoxygenase
Pea
Comparative study
Thermal stability
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Summary:Mature pea seeds contain two major lipoxygenases (LOX) isoenzymes designated LOX-2 and LOX-3. The thermal inactivation of crude pea LOX and the recombinant LOX (rLOX) were studied. Heat-inactivation plots for crude extracts of pea LOX were linear from which thermodynamic activation parameters, ΔH #, ΔS # sand ΔG # have been estimated. The enzymatic activity was relatively stable with a respective half-life ( t 1/2) at 60 °C of 54.2 min for LOX from pea ( Pisum sativum L. cv. Birte) or 18.4 min for a mutant line lacking LOX-2. At 50°C the thermostability of LOX-3 present in crude extracts of the mutant strain ( t 1/2=66.8 min) was 90% greater than purified recombinant LOX-3 (rLOX-3; t 1/2=34.6 min). However, rLOX-3 was more heat-stable than rLOX-2. Both rLOX-3 and pea mutant line lacking LOX-2 possessed considerable thermostability at 60°C ( t 1/2=16.5 min and 18.4 min, respectively). Even at the higher temperatures of 70°C the t 1/2 values were 84 and 51, respectively. It is suggested that LOX in crude enzyme extracts was stabilised at 50°C due to protection by other constituents, possibly including starch and proteins. Separate tests at 70°C in the presence of additives (polyols, detergents and small ions) showed that sucrose was the most effective stabiliser and increased the stability of pea LOX by 400–600%.
ISSN:0308-8146
1873-7072
DOI:10.1016/S0308-8146(98)00216-7