Activation of polyphenol oxidase in extracts of bran from several wheat (Triticum aestivum) cultivars using organic solvents, detergents, and chaotropes.
Polyphenol oxidase (PPO), known to induce browning in wheat-based products, has been shown to be activatable in wheat (Triticum aestivum) bran extracts by chemical compounds. The activity in the extracts could be increased to varying degrees with acetone, methanol, ethanol, 2-propanol, and n-butanol as additives in the extraction buffer. The most potent alcoholic activator was n-butanol (about a 3-fold increase), followed by 2-propanol and ethanol, whereas methanol had the least effect. Ionic detergents in the extraction buffer were also good activators, with sodium dodecyl sulfate (SDS) being more potent (3-fold increase) than cetyltrimethylammonium bromide (CTAB) that had only half as much effect, whereas the nonionic detergent, Triton X-114, was ineffective. The chaotropes, urea and guanidine x HCl (GND), were the most potent activators of all, increasing the activity over 4-fold. Of the two chaotropes, GND was more effective at lower concentrations (<6 M) than urea. However, the enzyme activity lessened at a higher concentration of GND (6 M), while there was a further increase in the activity with 6 M urea treatment. The activity lessened with higher concentration of GND presumably as a result of extensive denaturation of the enzyme, as GND is known to be a more potent denaturant than urea. It is hypothesized that in wheat PPO exists in an inactive form which may be activated by the presence of activators, hitherto unknown, similar in effect to that elicited by the chemical denaturants in this study.
Okot-Kotber
Moses
M
Department of Grain Science and Industry, Kansas State University, Manhattan, Kansas 66506, USA. bmo@wheat.ksu.edu.
Liavoga
Allan
A
Yong
Kwon-Joong
KJ
Bagorogoza
Katherine
K
D020001:1-Butanol / Q000494:pharmacology; D019840:2-Propanol / Q000494:pharmacology; D004156:Catechol Oxidase / Q000378:metabolism*; D003902:Detergents / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D000431:Ethanol / Q000494:pharmacology; D019791:Guanidine / Q000494:pharmacology*; D010936:Plant Extracts / Q000737:chemistry*; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D012997:Solvents; D014908:Triticum / Q000201:enzymology*; D014508:Urea / Q000494:pharmacology*
D003902:Detergents; D010936:Plant Extracts; D012997:Solvents; D012967:Sodium Dodecyl Sulfate; D000431:Ethanol; D020001:1-Butanol; D014508:Urea; D004156:Catechol Oxidase; D019791:Guanidine; D019840:2-Propanol