Electrophoretic analysis of effects of in vitro heating on proteins and enzymes from dormant peanuts (Arachis hypogaea)
Protein extracts from dormant peanut cotyledons were heated to determine the influence of different temperatures on banding characteristics of soluble proteins and enzymes by use of horizontal starch gel electrophoresis. Soluble proteins showed no significant change between 25° and 85 °C. At 95 °C, however, major bands of reserve protein decreased in staining intensity and new bands with greater migration velocity appeared; banding still occurred at 100 °C. Distribution patterns of glutamate dehydrogenase (GDH), malate dehydrogenase (MDH), nonspecific α-esterases (α-EST), and leucine aminopeptidase (LAP) reflected no change in banding or apparent enzyme activity at temperatures less than 45 °C. Complete inactivation was estimated for GDH at 80 to 85 °C, MDH at 65 °C, α-EST at 60 to 65 °C, and LAP at 60 to 65 °C. Isoenzymes of GDH, MDH, and LAP, and bands of α-EST exhibited differential thermal sensitivity. Peroxidase activity (using pyrogallol as the hydrogen donor) was not influenced through 65 °C; minimal reaction with benzidine occurred. No alkaline phosphatase activity was observed. Banding patterns of proteins or enzymes heated for 15 min were identical with those heated for 30 min. The results are compared with those of other studies regarding the influence of heat on proteins and enzymes in extracts of heated cotyledons from 5-day peanut seedlings and in extracts from wet- and dry-roasted seed.