Comparison of the biochemical properties and enzymatic synthesis of theaflavins by soluble and membrane-bound polyphenol oxidases from tea (Camellia sinensis) leaves

Abstract

Polyphenol oxidase (PPO) plays a key role in tea processing. It catalyzes the conversion of tea polyphenols into theaflavin and its derivatives. PPO was partially purified and characterized in both its soluble form (sPPO) and membrane-bound form (mPPO) from tea (Camellia sinensis) leaves. Both forms were purified by three-phase partitioning and membrane ultrafiltration. sPPO and mPPO showed high activity against diphenols as substrate and had the highest affinity for catechol and caffeic acid. The optimum temperatures and pH for enzyme activity were different. mPPO was more stable than sPPO in the acidic pH range. Among the chemical inhibitors studied, oxalic acid exerted the highest inhibitory effect on mPPO, whereas EDTA showed the highest inhibitory effect on sPPO. Both sPPO and mPPO showed similar enzymatic synthesis rates in the formation of theaflavin-3'-gallate and theaflavin-3,3'-gallate. At high concentrations of the substrate, the synthesis of theaflavins was inhibited due to the presence of high levels of ester catechins. However, mPPO showed stronger stability against inhibition by ester catechins than sPPO.

Recent Advances Regarding Polyphenol Oxidase in Camellia sinensis: Extraction, Purification, Characterization, and Application

“…Rapidly reducing salt ions in samples can also be achieved through ultrafiltration. Following TPP treatment, sPPO and mPPO in fresh tea leaves were centrifuged through an ultrafiltration tube (molecular weight cut-off of 15 kDa) using centrifugal force of 4500× g at 4 • C, and their purification times were found to increase by 9.58-fold and 9.05-fold, respectively [27].…”

Preparation of angiotensin I-converting enzyme (ACE) inhibitory peptides from Tie Guanyin tea residue protein using two-step enzymatic hydrolysis

“…Tea is one of the most popular functional beverages globally and rich source of polyphenols (Wang et al, 2022). Tea leaves contain multiple secondary metabolites, such as polyphenols, caffeine, and amino acids, which are important functional food and beneficial to human health (Liu et al, 2022b). The bioactive chemicals in Tie Guanyin and their functions have been widely investigated (Zhang et al, 2018).…”