Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634, USA.
Mol Plant. 2010 Mar;3(2):334-46. doi: 10.1093/mp/ssq003. Epub 2010 Feb 9.
Sequencing data from 10 species show that a plant hexokinase (HXK) family contains 5-11 genes. Functionally, a given family can include metabolic catalysts, glucose signaling proteins, and non-catalytic, apparent regulatory enzyme homologs. This study has two goals. The first aim is to develop a predictive method to determine which HXK proteins within a species have which type of function. The second aim is to determine whether HXK-dependent glucose signaling proteins occur among more primitive plants, as well as among angiosperms. Using a molecular phylogeny approach, combined with selective experimental testing, we found that non-catalytic HXK homologs might occur in all plants, including the relatively primitive Selaginella moellendorffi. We also found that different lineages of angiosperm HXKs have apparent conserved features for catalytic activity and for sub-cellular targeting. Most higher-plant HXKs are expressed predominantly at mitochondria, with HXKs of one lineage occurring in the plastid, and HXKs of one monocot lineage occurring in the cytosol. Using protoplast transient expression assays, we found that HXK glucose signaling proteins occur likely in all higher plants and in S. moellendorffi as well. Thus, the use of glucose by plant HXK isoforms in metabolism and/or as a regulatory metabolite occurs as widespread, conserved processes.
从 10 个物种的测序数据表明，植物己糖激酶 (HXK) 家族包含 5-11 个基因。在功能上，一个特定的家族可以包括代谢催化剂、葡萄糖信号蛋白和非催化的、明显的调节酶同源物。本研究有两个目标。第一个目标是开发一种预测方法，以确定一个物种内的哪些 HXK 蛋白具有哪种类型的功能。第二个目标是确定 HXK 依赖性葡萄糖信号蛋白是否存在于更原始的植物中，以及在被子植物中是否存在。我们使用分子系统发育方法，结合选择性实验测试，发现非催化 HXK 同源物可能存在于所有植物中，包括相对原始的卷柏。我们还发现，被子植物 HXK 的不同谱系具有催化活性和亚细胞靶向的明显保守特征。大多数高等植物 HXK 主要在线粒体中表达，一个谱系的 HXK 存在于质体中，一个单子叶植物谱系的 HXK 存在于细胞质中。通过原生质体瞬时表达测定，我们发现 HXK 葡萄糖信号蛋白可能存在于所有高等植物和卷柏中。因此，植物 HXK 同工型在代谢中以及作为调节代谢物使用葡萄糖的情况是广泛存在的保守过程。
