Incluye referencias bibliográficas

About the Author; 1: Introduction; References; 2: Distribution, Localization, and Structure of Plant Polyphenol Oxidases (PPOs); 2.1 Distribution and Localization of Plant PPOs; 2.1.1 Structure of Plant Polyphenol Oxidase; 2.2 Crystal Structure of Plant PPOs; 2.2.1 Structure of Sweet Potato (Ipomoea batatas) Catechol Oxidases; 2.2.2 Structure of Tickseed (Coreopsis grandiflora) Aurone Synthase (Catechol Oxidase); 2.2.3 Structure of Walnut (Juglans regia) Tyrosinase; References; 3: Physicochemical Properties of Polyphenol Oxidases; 3.1 Impact of pH on PPO Activity

3.2 Effects of Temperature on PPO Activity3.3 Substrate Specificity of PPOs; 3.4 Multiplicity of Plant PPOs; 3.5 Latency and Activation of PPOs; 3.6 Regulation of Polyphenol Oxidases; References; 4: Reaction Features of Polyphenol Oxidases; 4.1 Mechanism of Enzymatic Browning; 4.1.1 PPO Reaction Mechanism in N. crassa; 4.1.2 Reaction Mechanism of Catechol Oxidase from Ipomoea batatas; 4.1.3 Reaction Mechanism of Aurone Synthase from Coreopsis grandiflora; References; 5: Function(s)/Role(s) of Polyphenol Oxidases; 5.1 Role of PPOs in Plant Defense

5.1.1 Role of PPOs in Plant Resistance Against Pathogens5.1.2 Role of PPOs in Plant Resistance Against Insect Pests; 5.1.3 PPO Regulation in Response to Stress; 5.1.4 Mechanism of PPO Action in Plant Defense; 5.2 Role of PPOs in Biosynthesis of Specialized Metabolites; 5.2.1 Betalain Biosynthesis; 5.2.2 Aurone Biosynthesis; 5.2.3 Tyrosine Metabolism; 5.2.4 Lignan Biosynthesis; 5.2.5 Other Roles of PPOs in Plants; References; 6: Polyphenol Oxidase(s): Importance in Food Industry; 6.1 Control of Browning Reaction; 6.1.1 Chemical Control; 6.1.2 Physical Control; References

7: Advances in Polyphenol Oxidase (PPO) Research7.1 Genetic and Genomic Aspects of PPOs; 7.2 MicroRNA (miRNA) Technology in PPO; 7.3 miRNAs and Potato Tuber Browning; 7.4 miRNAs in Salvia miltiorrhiza; 7.5 Mutagenesis Studies of Polyphenol Oxidases; References

This book is first of its kind exclusively dedicated to plant polyphenol oxidases (PPOs), highlighting their importance in the food processing industry. By reviewing the scientific developments of the past several decades, it offers a comprehensive overview of various aspects of plant PPOs, including chemistry, structure, functions, regulation, genetics/genomics and molecular aspects. PPOs are copper-containing proteins found in several plant species that catalyze the hydroxylation of o-monophenols to o-diphenols and oxidation of the o-dihydroxyphenols to o-quinones. Further, the quonines undergo self-polymerization or react with amines/thiol groups to produce brown/dark coloration of products. All the PPOs contain two Cu-binding sites (CuA and CuB) as their central domain, these interact with phenolic substrates and molecular oxygen. Several of the plant PPOs contain an N-terminal transit peptide (̃80-100 amino acids ) necessary for plastid import. The PPOs occur in latent form that are activated by various treatments including acid and base shock, exposure to detergents or proteolytic degradation. The pH optimum of PPOs varies widely depending upon different plant species but is usually 4̃.0 - 8.0. Similarly, the optimum temperature also varies as per the source and substrate involved ranging from 30 to 45 °C. Multiple PPO isoforms have been reported in several plant species, and the chromosomal location of PPOs has also been studied in some species. The physiological role (s) of PPOs is not entirely understood, but they could be involved in defense-related functions in plants. From an applied perspective, PPOs are implicated in enzymatic browning/darkening of cereal products, vegetables and fruits. Interestingly, browning is preferred in some instances like the processing of black tea, cocoa, and coffee as it enhances their quality by forming flavorful products. There have been initiatives to specifically breed and develop cultivars with reasonably low PPO levels in the mature grain or fruit. Further, several types of inhibitors that reduce the PPO activity have also been identified. Despite their commercial/economic importance and the availability of literature on different aspects of PPOs in different plant species, this is the first book to provide basic information regarding PPOs. It is a valuable resource for researchers involved in quality-related research specifically in crops, vegetables and fruits. Further, as PPOs are also implicated in defense- or stress-related functions, the book is also useful to breeders, pathologists, molecular biologists, physiologists and entomologists.