Liu Chang-Jun
Biology Department, Brookhaven National Laboratory, Upton, NY, United States.
Front Plant Sci. 2022 Sep 23;13:984174. doi: 10.3389/fpls.2022.984174. eCollection 2022.
Cytochrome (CB5) is a small heme-binding protein, known as an electron donor delivering reducing power to the terminal enzymes involved in oxidative reactions. In plants, the CB5 protein family is substantially expanded both in its isoform numbers and cellular functions, compared to its yeast and mammalian counterparts. As an electron carrier, plant CB5 proteins function not only in fatty acid desaturation, hydroxylation and elongation, but also in the formation of specialized metabolites such as flavonoids, phenolic esters, and heteropolymer lignin. Furthermore, plant CB5s are found to interact with different non-catalytic proteins such as ethylene signaling regulator, cell death inhibitor, and sugar transporters, implicating their versatile regulatory roles in coordinating different metabolic and cellular processes, presumably in respect to the cellular redox status and/or carbon availability. Compared to the plentiful studies on biochemistry and cellular functions of mammalian CB5 proteins, the cellular and metabolic roles of plant CB5 proteins have received far less attention. This article summarizes the fragmentary information pertaining to the discovery of plant CB5 proteins, and discusses the conventional and peculiar functions that plant CB5s might play in different metabolic and cellular processes. Gaining comprehensive insight into the biological functions of CB5 proteins could offer effective biotechnological solutions to tailor plant chemodiversity and cellular responses to environment stimuli.
细胞色素b5（CB5）是一种小型血红素结合蛋白，作为电子供体，为参与氧化反应的末端酶提供还原能力。与酵母和哺乳动物中的细胞色素b5相比，植物中的CB5蛋白家族在异构体数量和细胞功能方面都有显著扩展。作为电子载体，植物CB5蛋白不仅在脂肪酸去饱和、羟基化和延长过程中发挥作用，还参与类黄酮、酚酯和杂聚物木质素等特殊代谢产物的形成。此外，人们发现植物CB5与乙烯信号调节剂、细胞死亡抑制剂和糖转运蛋白等不同的非催化蛋白相互作用，这表明它们在协调不同代谢和细胞过程中具有多种调节作用，可能与细胞氧化还原状态和/或碳可用性有关。与对哺乳动物CB5蛋白的生物化学和细胞功能的大量研究相比，植物CB5蛋白的细胞和代谢作用受到的关注要少得多。本文总结了与植物CB5蛋白发现相关的零散信息，并讨论了植物CB5在不同代谢和细胞过程中可能发挥的传统和特殊功能。全面了解CB5蛋白的生物学功能可为定制植物化学多样性和细胞对环境刺激的反应提供有效的生物技术解决方案。
