白茶萎凋过程中氨基酸类物质代谢分析

为研究白茶萎凋过程中氨基酸的变化,采用广泛靶向代谢组学及蛋白组学对0、12 h和30 h萎凋叶中氨基酸及相关酶进行检测。结果显示,游离氨基酸总量在萎凋前后无显著差异,萎凋前期（0~12 h）丝氨酸、亮氨酸、苯丙氨酸、赖氨酸、酪氨酸、组氨酸、异亮氨酸、脯氨酸、缬氨酸、苯丙氨酸、γ-氨基丁酸（GABA）含量上升,N-乙酰-L-谷氨酸、还原型谷胱甘肽、N-α-乙酰-L-精氨酸下降,萎凋后期（12~30 h）谷氨酸及乙酰甘氨酸含量减少;萎凋过程中蛋白质趋于降解,氨基酸合成途径相关的酶在萎凋前期（0~12 h）下调表达,氨基酸降解相关的酶在萎凋后期（12~30 h）上调表达;白茶萎凋过程中增加的蛋白质氨基酸主要来源于蛋白质水解,萎凋后期蛋白质氨基酸进一步转化为非蛋白质氨基酸,在失水条件下谷氨酸脱羧酶活性增强,促进γ-氨基丁酸含量增加。

Analysis of the Metabolism of Amino Acids during the Withering of White Tea

In order to investigate amino acids during the withering of white tea, metabolomics and proteomics were used to detect amino acids and related enzymes in the withered leaves at 0 h, 12 h and 30 h. The results show that the total amino acids had no significant change during withering process. While serine, leucine, phenylalanine, lysine, tyrosine, histidine, isoleucine, proline, valine, phenylalanine and γ-aminobutyric acid contents increased but N-acetyl-L-glutamic acid, reduced glutathione, N-α-acetyl-L-arginine decreased in the early stage of withering (0-12 h). The contents of glutamic acid and acetylglycine decreased in the later stage. Proteins tended to degrade during the withering process and the enzymes enriched in amino acid synthesis pathway were down-regulated in the early stage of withering, and the enzymes related to degradation were up-regulated in the later stage. The protein amino acids were mainly derived from protein hydrolysis, and then converted into non-protein amino acids. The γ-aminobutyric acid was regulated by glutamate decarboxylase under dehydration conditions. The increase of its content promoted the umami taste of white tea.