The chloroplastidal enzyme 2-phosphoglycolate phosphatase (PGLP), PGLP1, catalyzes the first reaction of the photorespiratory C2 cycle, a major pathway of plant primary metabolism. Thirteen potential PGLP genes are annotated in the Arabidopsis (Arabidopsis thaliana) genome; however, none of these genes has been functionally characterized, and the gene encoding the photorespiratory PGLP is not known. Here, we report on the identification of the PGLP1 gene in a higher plant and provide functional evidence for a second, nonphotorespiratory PGLP, PGLP2. Two candidate genes, At5g36700 (AtPGLP1) and At5g47760 (AtPGLP2), were selected by sequence similarity to known PGLPs from microorganisms. The two encoded proteins were overexpressed in Escherichia coli and both show PGLP activity. T-DNA knockout of one of these genes, At5g36700, results in very low leaf PGLP activity. The mutant is unviable in normal air but grows well in air enriched with 0.9% CO2. In contrast, deletion of At5g47760 does not result in a visible phenotype, and leaf PGLP activity is unaltered. Sequencing of genomic DNA from another PGLP-deficient mutant revealed a combined missense and missplicing point mutation in At5g36700. These combined data establish At5g36700 as the gene encoding the photorespiratory PGLP, PGLP1.
叶绿体酶2-磷酸甘氨酸磷酸酶(PGLP),PGLP1,催化光呼吸C2循环的第一个反应,是植物主要代谢途径之一。阿拉伯芥(Arabidopsis thaliana)基因组中注释了13个潜在的PGLP基因;然而,这些基因中没有一个被功能性地描述,且编码光呼吸PGLP的基因也不为人知。本文报告了高等植物PGLP1基因的鉴定,并提供了第二个非光呼吸性PGLP,PGLP2的功能证据。通过与微生物中已知PGLP的序列相似性选择了两个候选基因,At5g36700(AtPGLP1)和At5g47760(AtPGLP2)。这两个编码的蛋白质在大肠杆菌中过度表达,均表现出PGLP活性。其中一个基因At5g36700的T-DNA敲除导致叶片PGLP活性非常低。该突变体在正常空气中无法生存,但在富含0.9% CO2的空气中生长良好。相比之下,删除At5g47760并没有导致可见的表型,叶片PGLP活性也没有改变。从另一个PGLP缺陷突变体的基因组DNA测序中发现,在At5g36700中有一个联合错义和错剪点突变。这些数据共同证实了At5g36700是编码光呼吸PGLP,PGLP1的基因。