Journal of Animal and Plant Sciences
J. Anim. Plant Sci. [ISSN 2071 - 7024]
Volume 9 (3): 1169 -1179. Published February 28, 2011.
Study of some characteristics of soluble polyphenol oxidases from six cultivars callus of cassava (Manihot esculenta Crantz).
Seu Jonathan GOGBEU*1, Denezon Odette DOGBO1, Jean Tia GONNETY2, Boni N’ZUE3, Goli Pierre ZOHOURI3, Arsène BOKA1.
1Laboratoire de Biologie et Amélioration des Productions Végétales, Université d’Abobo-Adjamé, 02 BP 801 Abidjan 02, Côte d’Ivoire.
2Laboratoire de Biochimie et Technologie des Aliments, Université d’Abobo-Adjamé, 02 BP 801 Abidjan 02, Côte d’Ivoire.
3Programme plantes à racines et tubercules, Centre National de Recherche Agronomique (CNRA), 01 BP 1740 Abidjan 01, Côte d’Ivoire.
*Corresponding author. Fax: (+225)20304300, E-mail address: jgogbeu@yahoo.fr
Key words:
Cassava, callus, polyphenol oxidases, substrates, physicochemical parameters
SUMMARY
The objective was to study the influence of some physicochemical parameters on polyphenol oxidases (PPO) activities from callus of cassava (Manihot esculenta Crantz). The enzyme was extracted at different pH values, ranging from 2.0 to 11.0, and then treated with anion Dowex ®3% (w/v). The PPO activities were optimally active at pH range 4.5 to 8.0 and temperatures varying from 30 to 55 °C. The enzyme activity remained stable during the thermal treatment at 50 °C for 30 min but, at 100 °C, 60% of PPO activities were lost in most cultivars after 20 min. Catalytic efficiency (vmax/kM) calculated starting with 4 substrates (L-tyrosin, dopamine, pyrocatechol and pyrogallol) showed that dopamine (cultivars yacé, bonoua2 and I88/00158) and pyrocatechol (cultivars TMS4 (2)1425, TMS30572 and 9620A), were the best substrates of PPO. For these two diphenolic compounds, PPO activities were 1.2 to 1.8 times stimulated in the presence of 5 to 10 mM of the ions Ca2+ and Cu2+. At the same concentrations, Mg2+ and Zn2+ had almost no effect on the enzymes.
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