Institute of Fruit Tree Research, Guangdong Academy of Agricultural Sciences; Key Laboratory of South Subtropical Fruit Biology and Genetic Resource Utilization, Ministry of Agriculture and Rural Affairs; Guangdong Provincial Key Laboratory of Science and Technology Research on Fruit Trees, Guangzhou, 510640, China; College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.
College of Horticulture, South China Agricultural University, Guangzhou 510642, China; State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources / Guangdong Provincial Key Laboratory of Postharvest Science of Fruit and Vegetables / Engineering Research Center for Postharvest Technology of Horticultural Crops in South China, South China Agricultural University, Guangzhou 510642, China.
Food Chem. 2024 Dec 15;461:140937. doi: 10.1016/j.foodchem.2024.140937. Epub 2024 Aug 20.
The longan pericarp turns brown dramatically after harvesting, but the mechanism is not well understood. In this work, two peroxidases were purified from longan pericarp and found to be identical to the class III peroxidases PRX53-2 and PRX53-3. In vitro, PRX53-2/3 catalyzed the browning of several pericarp abundant proanthocyanidin and lignin monomers, such as (-)-epicatechin (EC), (+)-catechin (CT) and coniferyl alcohol (ConA). PRX53-2 was upregulated and highly-expressed, while PRX53-3 was expressed at low levels after harvesting; thus, PRX53-2 was considered a browning-related gene. The reaction with both proanthocyanidin and lignin presented a greater degree of brown coloration compared to the single substrate reactions. Several procyanidins isomers, EC-ConA and CT-ConA were detected in the double-substrate reaction. These results not only demonstrate that the effects of PRX53-2 on proanthocyanidin and lignin polymerization may be crucial for longan pericarp browning, but also help in developing new strategies or preservatives to delay pericarp browning.
龙眼果皮在收获后会迅速变成褐色，但机理尚不清楚。本研究从龙眼果皮中纯化得到了两种过氧化物酶，鉴定为与 PRX53-2 和 PRX53-3 相同的 III 类过氧化物酶。体外实验表明，PRX53-2/3 可以催化几种果皮中丰富的原花青素和木质素单体的褐变，如（-）-表儿茶素（EC）、（+）-儿茶素（CT）和松柏醇（ConA）。收获后，PRX53-2 上调并高度表达，而 PRX53-3 表达水平较低；因此，PRX53-2 被认为与褐变有关。与单一底物反应相比，过氧化物酶与原花青素和木质素的反应呈现出更大程度的褐色。在双底物反应中检测到几种原花青素异构体、EC-ConA 和 CT-ConA。这些结果不仅表明 PRX53-2 对原花青素和木质素聚合的影响可能对龙眼果皮褐变至关重要，还有助于开发新的策略或防腐剂来延缓果皮褐变。
