Roy J. Carver Department of Biochemistry, Biophysics & Molecular Biology, Iowa State University, Ames, IA, 50011, United States.
Roy J. Carver Department of Biochemistry, Biophysics & Molecular Biology, Iowa State University, Ames, IA, 50011, United States.
Phytochemistry. 2021 Apr;184:112672. doi: 10.1016/j.phytochem.2021.112672. Epub 2021 Jan 29.
All land plants (embryophytes) must contain an ent-kaurene synthase (KS), as the ability to produce this olefin from ent-copalyl diphosphate (ent-CPP) is required for phytohormone biosynthesis. These KSs have frequently given rise to other class I diterpene synthases that catalyze distinct reactions for more specialized plant metabolism. Indeed, the prevalence of such gene duplication and neofunctionalization has obscured phylogenetic assignment of function. Here a pair of threonines is found to be conserved in all land plant KS involved in phytohormone biosynthesis, and their role in enzyme function investigated. Surprisingly, these threonines are not required, nor even particularly important for efficient production of ent-kaurene from ent-CPP. In addition, these threonines do not seem to affect protein structure or stability. Moreover, the absence of codon bias and positioning within an intron do not support a role in transcription or translation either. Despite their lack of apparent function, this pair of threonines are nevertheless completely conserved in all embryophyte KS from phytohormone biosynthesis. Thus, regardless of exact role, this serves as a diagnostic mark for such KS, enabling more confident distinction of these critical enzymes.
所有陆地植物（胚胎植物）都必须含有一种 ent-贝壳杉烯合酶（KS），因为从 ent-贝壳杉烯二磷酸酯（ent-CPP）产生这种烯烃是植物激素生物合成所必需的。这些 KS 经常产生其他的 I 类二萜合酶，这些酶催化不同的反应，以满足更专门的植物代谢需求。事实上，这种基因重复和新功能化的普遍性掩盖了功能的系统发育分配。在这里，在所有参与植物激素生物合成的陆地植物 KS 中发现了一对苏氨酸是保守的，并研究了它们在酶功能中的作用。令人惊讶的是，这些苏氨酸既不是必需的，也不是从 ent-CPP 高效生产 ent-贝壳杉烯所必需的。此外，这些苏氨酸似乎不影响蛋白质结构或稳定性。此外，在一个内含子内不存在密码子偏好和定位也不支持转录或翻译的作用。尽管它们似乎没有明显的功能，但这对苏氨酸在所有参与植物激素生物合成的胚胎植物 KS 中仍然是完全保守的。因此，无论确切的作用如何，这都可以作为这些 KS 的一个诊断标记，使这些关键酶的区分更加有信心。
