Purification and Properties of a Neutral Peroxidase Isozyme from Turnip (Brassica napus L. Var. Purple Top White Globe) Roots

• Published in: Journal of agricultural and food chemistry Vol. 49; no. 9; pp. 4450 - 4456
• Main Authors: Duarte-Vázquez, Miguel A, García-Almendárez, Blanca E, Regalado, Carlos, Whitaker, John R
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.09.2001
• Subjects: Biological and medical sciences; Biotechnology; Brassica - enzymology; Enzyme engineering; Food industries; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Improved methods for extraction and purification of enzymes; Isoenzymes; Kinetics; Methods. Procedures. Technologies; Molecular Weight; Peroxidase - isolation & purification; Peroxidase - metabolism; Production quality; Isozyme; Organoleptic properties; Subunit; Specific activity; Characterization; Enzymatic activity; Cruciferae; Dicotyledones; Angiospermae; Peroxidase; Activation energy; Molecular mass; Purification; Root; Enzyme; Armoracia rusticana; Peroxidases; Vegetable crop; Brassica napus; Flavoring crop; Spermatophyta; Oxidoreductases; Catalyst activity; Optimum pH; Comparative study
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf010043e

A neutral peroxidase isozyme (pI 7.2) from turnip roots (TNP) was purified to homogeneity and partially characterized. TNP is a monomeric glycoprotein with 9.1% carbohydrate content and a molecular weight of 36 kDa. Optimum pH values for activity using 2,2‘-azinobis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) and guaiacol as H donors were 4.5 and 5.5, whereas the K m values were 0.7 and 3.7 mM, respectively. The ABTS K m was ∼7 times higher than that reported for basic commercial horseradish peroxidase (HRP-C). TNP retained ∼70% activity after 11 min of heating at 65 °C, whereas the activation energy for inactivation (132 kJ/mol) was higher than or comparable to that of other peroxidases. The low ABTS K m and high specific activity (1930 units/mg) gave a high catalytic efficiency (500 M-1 s-1). These properties make TNP an enzyme with a high potential as an alternative to HRP in various applications. Keywords: Neutral peroxidase; turnip roots; protein purification