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Horticulturae
Volume 12
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10.3390/horticulturae12010037
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Article

Enzymatic Characterization and Biological Function Analysis of Tannases JrTA1 and JrTA2 in Walnut (Juglans regia L.)

by
Hui Liu
1,
Xiong Zheng
1,
Chang Liu
1,
Guihua Chen
1,
Yanyu Shi
1,
Jinghua Xu
1,
Yuhao Zhang
1,
Yan Gao
1,2,
Xiaojun Zhang
1,2,* and
Qunlong Liu
1,2,*
1
College of Horticulture, Shanxi Agricultural University, Jinzhong 030801, China
2
Shanxi Provincial Key Laboratory of Fruit Tree Germplasm Creation and Utilization, Taiyuan 030031, China
*
Authors to whom correspondence should be addressed.
Horticulturae 2026, 12(1), 37; https://doi.org/10.3390/horticulturae12010037 (registering DOI)
Submission received: 14 November 2025 / Revised: 19 December 2025 / Accepted: 25 December 2025 / Published: 27 December 2025
(This article belongs to the Section Developmental Physiology, Biochemistry, and Molecular Biology)
Versions Notes

Abstract

Tannins are key compounds determining the astringency of walnuts. Elucidating the structural characteristics of tannin cells in walnut inner seed coats and the accumulation patterns of esterified catechins (e.g., EGCG and ECG) is of significant importance for both quality regulation of walnuts and the high-value utilization of tannin resources. However, the enzymatic properties and biological functions of walnut tannases (JrTAs) have not been systematically investigated. Thus, the enzymatic characteristics of walnut tannase and its hydrolytic function on tannin-like substances were analyzed. It showed that tannin accumulation in the inner seed coat of ‘Nonghe 1′ walnut was closely associated with the development of tannin cells. During seed coats development, the total tannin content initially decreased and then increased, while the levels of monomeric phenolics related to tannin synthesis (GC, EGC and EC) continuously increased. Two walnut tannase genes, JrTA1 and JrTA2, were cloned and the recombinant proteins were purified. In vitro enzymatic activity tests confirmed that both enzymes effectively hydrolyzed ester-type catechins ECG and EGCG after 20 min of reaction at 40 °C and pH 7.0. Moreover, the transgenic Arabidopsis systems and green tea infusion study demonstrated that JrTA1 and JrTA2 retained their ability to specifically cleave the ester bonds of ester-type catechins in heterologous systems, achieving efficient tannin degradation. This study systematically elucidates the enzymatic functions of JrTAs, which provides a theoretical foundation for the further development and application of walnut tannases.
Keywords: walnut; JrTAs; tannase; prokaryotic expression; enzymatic properties walnut; JrTAs; tannase; prokaryotic expression; enzymatic properties

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MDPI and ACS Style

Liu, H.; Zheng, X.; Liu, C.; Chen, G.; Shi, Y.; Xu, J.; Zhang, Y.; Gao, Y.; Zhang, X.; Liu, Q. Enzymatic Characterization and Biological Function Analysis of Tannases JrTA1 and JrTA2 in Walnut (Juglans regia L.). Horticulturae 2026, 12, 37. https://doi.org/10.3390/horticulturae12010037

AMA Style

Liu H, Zheng X, Liu C, Chen G, Shi Y, Xu J, Zhang Y, Gao Y, Zhang X, Liu Q. Enzymatic Characterization and Biological Function Analysis of Tannases JrTA1 and JrTA2 in Walnut (Juglans regia L.). Horticulturae. 2026; 12(1):37. https://doi.org/10.3390/horticulturae12010037

Chicago/Turabian Style

Liu, Hui, Xiong Zheng, Chang Liu, Guihua Chen, Yanyu Shi, Jinghua Xu, Yuhao Zhang, Yan Gao, Xiaojun Zhang, and Qunlong Liu. 2026. "Enzymatic Characterization and Biological Function Analysis of Tannases JrTA1 and JrTA2 in Walnut (Juglans regia L.)" Horticulturae 12, no. 1: 37. https://doi.org/10.3390/horticulturae12010037

APA Style

Liu, H., Zheng, X., Liu, C., Chen, G., Shi, Y., Xu, J., Zhang, Y., Gao, Y., Zhang, X., & Liu, Q. (2026). Enzymatic Characterization and Biological Function Analysis of Tannases JrTA1 and JrTA2 in Walnut (Juglans regia L.). Horticulturae, 12(1), 37. https://doi.org/10.3390/horticulturae12010037

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