A comprehensive review of polyphenol oxidase in tea (Camellia sinensis): Physiological characteristics, oxidation manufacturing, and biosynthesis of functional constituents.

Polyphenol oxidase (PPO) is a metalloenzyme with a type III copper core that is abundant in nature. As one of the most essential enzymes in the tea plant (Camellia sinensis), the further regulation of PPO is critical for enhancing defensive responses, cultivating high-quality germplasm resources of tea plants, and producing tea products that are both functional and sensory qualities. Due to their physiological and pharmacological values, the constituents from the oxidative polymerization of PPO in tea manufacturing may serve as functional foods to prevent and treat chronic non-communicable diseases. However, current knowledge of the utilization of PPO in the tea industry is only available from scattered sources, and a more comprehensive study is required to reveal the relationship between PPO and tea obviously. A more comprehensive review of the role of PPO in tea was reported for the first time, as its classification, catalytic mechanism, and utilization in modulating tea flavors, compositions, and nutrition, along with the relationships between PPO-mediated enzymatic reactions and the formation of functional constituents in tea, and the techniques for the modification and application of PPO based on modern enzymology and synthetic biology are summarized and suggested in this article.

Enhanced activity and substrate tolerance of 7α-hydroxysteroid dehydrogenase by directed evolution for 7-ketolithocholic acid production.

7-Ketolithocholic acid (7-KLCA) is an important intermediate for the synthesis of ursodeoxycholic acid (UDCA). UDCA is the main effective component of bear bile powder that is used in traditional Chinese medicine for the treatment of human cholesterol gallstones. 7α-Hydroxysteroid dehydrogenase (7α-HSDH) is the key enzyme used in the industrial production of 7-KLCA. Unfortunately, the natural 7α-HSDHs reported have difficulty meeting the requirements of industrial application, due to their poor activities and strong substrate inhibition. In this study, a directed evolution strategy combined with high-throughput screening was applied to improve the catalytic efficiency and tolerance of high substrate concentrations of NADP+-dependent 7α-HSDH from Clostridium absonum. Compared with the wild type, the best mutant (7α-3) showed 5.5-fold higher specific activity and exhibited 10-fold higher and 14-fold higher catalytic efficiency toward chenodeoxycholic acid (CDCA) and NADP+, respectively. Moreover, 7α-3 also displayed significantly enhanced tolerance in the presence of high concentrations of substrate compared to the wild type. Owing to its improved catalytic efficiency and enhanced substrate tolerance, 7α-3 could efficiently biosynthesize 7-KLCA with a substrate loading of 100 mM, resulting in 99% yield of 7-KLCA at 2 h, in contrast to only 85% yield of 7-KLCA achieved for the wild type at 16 h.

[Correlation study on effects of electroacupuncture on the muscle condition and MNCV in rabbits with lumbar nerve root compression].

OBJECTIVE: To observe the effects of electroacupuncture on the muscle condition and electrophysiology of the muscle in rabbits with lumbar nerve root compression and to explore potential mechanisms. METHODS: Twenty-four New Zealand white rabbits were randomly divided into a normal group, a model group, a medication group and an electroacupuncture group. The rabbit model with lumbar nerve root compression was established in the model group, the medication group and the electroacupuncture group. The model and the treatment were not produced in the normal group. The medication group was treated with oral administration of Loxoprofen tablets at a dose of 30 mg each day for 14 days. The electroacupuncture group was treated with electroacupuncture at "Jiaji" (EX-B 2) of L5 and L6 for 14 days. The hibateral muscle condition before and after making model and after treatment was detected and the electromyogram and the nerve conduction velocity (NCV) were observed. RESULTS: The spontaneous potential and the insertion potential were increased in the model group, the medication group and the electroacupuncture group after making model. The value of the activation and the relaxed condition of the strength-creep (ARCSC) in the right muscle was significantly decreased. The motor nerve conduction velocity (MNCV) and the wave amplitude of evoked potential (WAEP) were significantly decreased in the model group, the medication group and the electroacupuncture group after treatment, but the value of MNCV and WAEP in the electroacupuncture group, and ARCSC in the right muscle in the electroacupuncture group and the medicine group were closed to those level in the normal group, among them, the relaxed condition in the electroacupuncture group was more close to the level in the normal group. CONCLUSION: Electroacupuncture can improve the strength-creep condition of the muscle that damage nerve place controls and the electrophysiology of the muscle can recover the MNCV and the wave amplitude of evoked potential in the compression nerve root.