Parallel Strategy Increases the Thermostability and Activity of Glutamate Decarboxylase.

Glutamate decarboxylase (GAD; EC 4.1.1.15) is a unique pyridoxal 5-phosphate (PLP)-dependent enzyme that specifically catalyzes the decarboxylation of L-glutamic acid to produce γ-aminobutyric acid (GABA), which exhibits several well-known physiological functions. However, glutamate decarboxylase from different sources has the common problem of poor thermostability that affects its application in industry. In this study, a parallel strategy comprising sequential analysis and free energy calculation was applied to identify critical amino acid sites affecting thermostability of GAD and select proper mutation contributing to improve structure rigidity of the enzyme. Two mutant enzymes, D203E and S325A, with higher thermostability were obtained, and their semi-inactivation temperature (T5015) values were 2.3 °C and 1.4 °C higher than the corresponding value of the wild-type enzyme (WT), respectively. Moreover, the mutant, S325A, exhibited enhanced activity compared to the wild type, with a 1.67-fold increase. The parallel strategy presented in this work proved to be an efficient tool for the reinforcement of protein thermostability.

[Noise-reduction function and its affecting factors of urban plant communities in Shanghai].

The factor analysis on the relationships between excess noise attenuation (decrement after noise propagating 30 m) and 8 structural characteristics of 19 urban plant communities in Shanghai showed that all the plant communities had notable effects on reducing noise, and the noise attenuation ability of the communities was significantly higher than that of lawn (P < 0.01). The plant communities could be divided into three groups base on their noise attenuation ability, i.e., those of > or = 10 dB(A), 6-10 dB(A), and < or = 6 dB(A). The main factors affecting the noise attenuation ability of the communities were leaf area index, average bifurcate height, average height, coverage, and average canopy diameter, and their correlation coefficients with noise attenuation were 0.343, 0.318, 0.285, 0.226 and 0.193, respectively. These five factors had a cumulative contribution rate of 65.47%, suggesting that they should be considered in stress when designing urban greenbelt for noise reduction.