Journal
INTERNATIONAL JOURNAL OF FOOD PROPERTIES
Volume 14, Issue 4, Pages 809-821Publisher
TAYLOR & FRANCIS INC
DOI: 10.1080/10942910903453363
Keywords
Polyphenol oxidase; (Cynara scolymus L; ); Artichoke head; Artichoke leaves; Thermal stability; Kinetic
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Funding
- Trakya University [TUBAP-621]
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Artichoke polyphenol oxidases (PPOs) were obtained by (NH4)2SO4 precipitation using ascorbic acid, polyvinylpyrrolidone, and Triton X-100. The PPO content of artichoke head (AHPPO) was 8820 units (mg protein)-1 as compared with 3370 units (mg protein)-1 in artichoke leaves-and-stem (ALSPPO) by using catechol as a substrate. The substrates of both AHPPO and ALSPPO are o-diphenols, such as catechol, pyrogallol, and L-DOPA. Optimum pH and temperature of both PPOs were determined. AHPPO had higher thermal stability than ALSPPO. Also, Tm (the midpoint of thermal inactivation) and t1/2 (half-life) values were determined. Km and Vmax of both PPOs were observed to be similar. Twelve inhibitors were tested and their I50 values were determined. The most effective inhibitors were found to be potassium cyanide, ascorbic acid, L-cysteine, and thiourea. Sodiumdodecylsulfate, urea, and cupric sulfate caused an increase about 20-30% in the PPO activity.
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