Browning inAnnona cherimolaFruit: Role of Polyphenol Oxidase and Characterization of a Coding Sequence of the Enzyme

Abstract

Cherimoya (Annona cherimola Mill.) fruit is an attractive candidate for food processing applications as fresh cut. However, along with its desirable delicate taste, cherimoya shows a marked susceptibility to browning. This condition is mainly attributed to polyphenol oxidase activity (PPO). A general lack of knowledge regarding PPO and its role in the oxidative loss of quality in processed cherimoya fruit requires a better understanding of the mechanisms involved. The work carried out included the cloning of a full-length cDNA, an analysis of its properties in the deduced amino sequence, and linkage of its mRNA levels with enzyme activity in mature and ripe fruits after wounding. The results showed one gene different at the nucleotide level when compared with previously reported genes, but a well-conserved protein, either in functional and in structural terms. Cherimoya PPO gene (Ac-ppo, GenBank DQ990911) showed to be present apparently in one copy of the genome, and its transcripts could be significantly detected in leaves and less abundantly in flowers and fruits. Analysis of wounded matured and ripened fruits revealed an inductive behavior for mRNA levels in the flesh of mature cherimoya after 16 h. Although the highest enzymatic activity was observed on rind, a consistent PPO activity was detected on flesh samples. A lack of correlation between PPO mRNA level and PPO activity was observed, especially in flesh tissue. This is probably due to the presence of monophenolic substrates inducing a lag period, enzyme inhibitors and/or diphenolic substrates causing suicide inactivation, and proenzyme or latent isoforms of PPO. To our knowledge this is the first report of a complete PPO sequence in cherimoya. Furthermore, the gene is highly divergent from known nucleotide sequences but shows a well conserved protein in terms of its function, deduced structure, and physiological role.

The polyphenol oxidase gene family in poplar: phylogeny, differential expression and identification of a novel, vacuolar isoform

“…Introns may inXuence gene expression of PPO isoforms via alternative splicing, as was recently demonstrated for a PPO isoform in wheat (Sun et al 2011). Recently, an intron-containing PPO gene was reported from a dicot species, AcPPO from cherimoya (Prieto et al 2007). Like PtrPPO13, AcPPO also has an N-terminal signal sequence rather than a cTP, and both sequences group together in the phylogeny (Fig.…”

“…Introns are uncommon in most characterized PPO genes and have only been reported in a few monocot PPOs and Physcomitrella patens Pp_PPO1 (Richter et al 2005). However, an intron is present in the cherimoya AcPPO gene, one of the top hits in Genbank (Prieto et al 2007; see below). To conWrm the presence of the intron and to determine the correct gene model for PtrPPO13, gene-speciWc primers were used to amplify both the 5Ј and 3Ј ends, as well as the complete 1,764-bp PtrPPO13 cDNA.…”

“…The 163 bp intron is shaded gray. Bold residues represent identical amino acids in cherimoya AcPPO (Prieto et al 2007). Together, these sequences share 51% amino acid identity.…”

El efecto antisenescente del resveratrol reduce la tasa de ablandamiento poscosecha de chirimoya

“…En este sentido, la significancia reportada tiene que ver más con la madurez per se, que por la aplicación de RVS. Como se sabe, el bronceado de la cáscara de chirimoya se debe a la oxidación enzimática irreversible causada por la polifenol oxidasa (PPO) y la peroxidada (POD) (Prieto et al, 2007), por lo tanto, se considera que en este trabajo RVS no tuvo el efecto de inhibir dichas enzimas.…”

Polyphenol Oxidase in Pawpaw (Asimina triloba [L.] Dunal) Fruit Pulp from Different Varieties

“…o-quinones during ripening and postharvest handling, storage and processing. In Annonaceous fruits, PPO activity has been determined for atemoya (Chaves, Ferreira, Da Silva, & Neves, 2011), cherimoya (Prieto et al, 2007), soursop (Deoliviera, Guerra, Maciel, & Liveri, 1994;Falguera, et al, 2012), and sugar apple (Wu, 2000). Currently, there is a single published study on the activity of PPO in pawpaw (Fang et al, 2007).…”