茶树中特定丙氨酸脱羧酶及其祖先丝氨酸脱羧酶的生化特征

Biochemical characterization of specific Alanine Decarboxylase (AlaDC) and its ancestral enzyme Serine Decarboxylase (SDC) in tea plants (Camellia sinensis)

第一作者

Peixian Bai 和 Liyuan Wang

第一单位

中科院茶叶研究所

通讯作者

Dejiang Ni 和 Hao Cheng

Abstract

背景+问题：AlaDC, specifically present in tea plants, is crucial for theanine biosynthesis. SDC, found in many plants, is a protein most closely related to AlaDC.

主要研究：To investigate whether the new gene AlaDC originate from gene SDC and to determine the biochemical properties of the two proteins from Camellia sinensis, the sequences of CsAlaDC and CsSDC were analyzed and the two proteins were over-expressed, purified, and characterized.

结果1：Exon-intron structures of AlaDC and SDC were quite similar and the protein sequences, encoded by the two genes, shared a high similarity of 85.1%, revealing that new gene AlaDC originated from SDC by gene duplication.

结果2：CsAlaDC and CsSDC catalyzed the decarboxylation of alanine and serine, respectively. CsAlaDC and CsSDC exhibited the optimal activities at 45 °C (pH 8.0) and 40 °C (pH 7.0), respectively. CsAlaDC was stable under 30 °C (pH 7.0) and CsSDC was stable under 40 °C (pH 6.0–8.0). The activities of the two enzymes were greatly enhanced by the presence of pyridoxal-5′-phosphate. The specific activity of CsSDC was 8.8-fold higher than that of CsAlaDC.

结论：Comparing to CsAlaDC, its ancestral enzyme CsSDC exhibited a higher specific activity and a better thermal and pH stability, indicating that CsSDC acquired the optimized function after a longer evolutionary period. The biochemical properties of CsAlaDC might offer reference for theanine industrial production.

摘  要

背景

茶树中专门存在的丙氨酸脱羧酶对于茶氨酸的生物合成至关重要。在许多植物中发现的丝氨酸脱羧酶是与AlaDC最密切相关的蛋白质。为了研究新基因AlaDC是否源自SDC基因并确定山茶中这两种蛋白质的生化特性，分析了CsAlaDC和CsSDC的序列，并过表达，纯化和表征了这两种蛋白质。

结果

结果表明，AlaDC和SDC的外显子-内含子结构非常相似，由两个基因编码的蛋白质序列具有85.1％的高度相似性，表明新基因AlaDC通过基因复制源自SDC。CsAlaDC和CsSDC分别催化丙氨酸和丝氨酸的脱羧。CsAlaDC和CsSDC分别在45 C（pH 8.0）和40 C（pH 7.0）下表现出最佳活性。CsAlaDC在30°C（pH 7.0）下稳定，而CsSDC在40°C（pH 6.0-8.0）下稳定。吡ido醛-5'-磷酸的存在极大地增强了这两种酶的活性。CsSDC（30,488 IU / mg）的比活性是CsAlaDC（3467 IU / mg）的比活性的8.8倍。

结论

与CsAlaDC相比，其祖先酶CsSDC表现出更高的比活性以及更好的热稳定性和pH稳定性，表明CsSDC在更长的进化时期后获得了优化的功能。CsAlaDC的生化特性可能为茶氨酸工业生产提供参考。

https://doi.org/10.1186/s12896-021-00674-x

Journal: BMC Biotechnology 

Impact Factor：2.3

Published date: 01 March 2021

END

三月

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