Molecular cloning and characterization of the polyphenol oxidase gene from sweetpotato

作者：Zhihua Liao, Ruyi Chen, M. Chen, Yihao Yang, Yao Fu, Qingwei Zhang, Xiaozhong Lan · 发表于：Molecular Biology · 年份：2006 · DOI：10.1134/s0026893306060094 · 被引用次数：18 · 研究领域：Postharvest Quality and Shelf Life Management、Enzyme-mediated dye degradation、Biochemical and biochemical processes

Polyphenol oxidase is the enzyme responsible for enzymatic browning in sweetpotato that decreases the commercial value of sweetpotato products. Here we reported the cloning and characterization of a new cDNA encoding PPO from sweetpotato, designated as IbPPO (GeneBank accession number: AY822711). The full-length cDNA of IbPPO is 1984 bp with a 1767 bp open reading frame (ORF) encoding a 588 amino acid polypeptide with a calculated molecular weight of 65.7 kDa and theoretical pI of 6.28. The coding sequence of IbPPO was also directly amplified from the genomic DNA of sweetpotato that demonstrated that IbPPO was an intron-free gene. The computational comparative analysis revealed that IbPPO showed homology to other PPOs of plant origin and contained a 50 amino acid plastidial transit peptide at its N-terminal and the two conserved CuA and CuB copper-binding motifs in the catalytic region of IbPPO . A highly conserved serine-rich motif was firstly found in the transit peptides of plant PPO enzymes. Then the homology based structural modeling of IbPPO showed that IbPPO had the typical structure of PPO: the catalytic copper center was accommodated in a central four-helix bundle located in a hydrophobic pocket close to the surface. Finally, the results of the semiquantitative RT-PCR analysis of IbPPO in different tissues demonstrated that IbPPO could express in all the organs of sweetpotato including mature leaves, young leaves, the stems of mature leaves (petioles), the storage ro...