Abstract
Polyphenol oxidase from apricot (Prunus armeniaca) (PaPPO) was purified in its latent form (L-PaPPO), and the molecular weight was determined to be 63 kDa by SDS-PAGE. L-PaPPO was activated in the presence of substrate at low pH. The activity was enhanced by CuSO4 and low concentrations (≤ 2 mM) of SDS. PaPPO has its pH and temperature optimum at pH 4.5 and 45 °C for catechol as substrate. It showed diphenolase activity and highest affinity toward 4-methylcatechol (KM = 2.0 mM) and chlorogenic acid (KM = 2.7 mM). L-PaPPO was found to be spontaneously activated during storage at 4 °C, creating a new band at 38 kDa representing the activated form (A-PaPPO). The mass of A-PaPPO was determined by mass spectrometry as 37 455.6 Da (Asp102 → Leu429). Both L-PaPPO and A-PaPPO were identified as polyphenol oxidase corresponding to the known PaPPO sequence (UniProt O81103) by means of peptide mass fingerprinting.
Highlights
Apricot (Prunus armeniaca L.) is one of the most delicious and important crops in the Mediterranean region and is consumed worldwide
L-PPO. Apricot PPO (PaPPO) was found to be spontaneously activated during storage at 4 °C, creating a new band at 38 kDa representing the activated form (A-PaPPO)
Both L-PaPPO and activity for PaPPO after storage (A-PaPPO) were identified as polyphenol oxidase corresponding to the known PaPPO sequence (UniProt O81103) by means of peptide mass fingerprinting
Summary
Apricot (Prunus armeniaca L.) is one of the most delicious and important crops in the Mediterranean region and is consumed worldwide. The optimum temperature for PaPPO activity was determined in 600 μL of assay mixture, containing 1.5 μg of enzyme and 10 mM catechol in 50 mM citrate buffer (pH 4.5).
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