Kinetics of thermal inactivation of pea seed lipoxygenases and the effect of additives on their thermostability
| Autor: | J Casey, Richard K. Owusu Apenten, María D. Busto, Richard K. Hughes, Zencai Wu, David S. Robinson |
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| Rok vydání: | 1999 |
| Předmět: |
musculoskeletal diseases
Sucrose endocrine system diseases Starch Analytical Chemistry Pisum law.invention chemistry.chemical_compound Lipoxygenase Sativum law Food science Thermostability chemistry.chemical_classification integumentary system biology food and beverages General Medicine biology.organism_classification enzymes and coenzymes (carbohydrates) Enzyme chemistry Biochemistry biology.protein Recombinant DNA Food Science |
| Zdroj: | Food Chemistry. 65:323-329 |
| ISSN: | 0308-8146 |
| DOI: | 10.1016/s0308-8146(98)00216-7 |
| Popis: | 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%. |
| Databáze: | OpenAIRE |
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