γ-Glutamyl transpeptidase (GGT) in Toona sinensis shoot (TS) was extracted and purified through salt precipitation, ion-exchange column, and gel filtration chromatography methods. The GGT had two peptides with M.W. 35 and 50 kDa. Its function in the formation of TS sulfur-containing volatiles (SCVs) was evaluated. The highest GGT hydrolytic activity was at pH 7.0 and 50 °C. Its activity was enhanced by Ca²⁺, Mg²⁺, K⁺, Na⁺, and Ba²⁺ and reduced by Cu²⁺, Fe³⁺, Mn²⁺, and Zn²⁺. The SCVs reached the highest level at GGT to TS sulfur-containing precursors extract 1:20. The aroma produced by GGT from the extract was similar to that of raw TS, especially for the cooked onion-like/TS-like flavor. These results revealed the characteristics and function of GGT in TS on sulfurous aroma formation. It could be applied to retrieve the production of sulfur-containing aroma from thermally preserved TS or similar vegetables, which lost GGT activity irreversibly during heat drying.

中文翻译：

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香椿 γ-谷氨酰转肽酶的纯化与表征及其对含硫挥发物形成的作用


采用盐沉淀、离子交换柱和凝胶过滤色谱法提取和纯化香椿茎 （TS） 中的 γ-谷氨酰转肽酶 （GGT）。GGT 有 M.W. 35 和 50 kDa 的两种肽。评估了它在形成 TS 含硫挥发物 （SCV） 中的功能。GGT 水解活性最高，在 pH 7.0 和 50 °C 时。 Ca²⁺、Mg²⁺、K⁺、Na⁺ 和 Ba²⁺ 增强了其活性，Cu²⁺、Fe³⁺、Mn²⁺ 和 Zn²⁺ 降低了其活性。SCV 在 GGT 至 TS 含硫前体提取物 1：20 时达到最高水平。GGT 从提取物中产生的香气与生 TS 相似，尤其是煮熟的洋葱样/TS 样风味。这些结果揭示了 TS 中 GGT 对亚磺香气形成的特征和功能。它可用于从热保存的 TS 或类似蔬菜中回收含硫香气的产生，这些蔬菜在热干燥过程中不可逆地失去了 GGT 活性。