Speiser D M, Ortiz D F, Kreppel L, Scheel G, McDonald G, Ow D W
Plant Gene Expression Center, U.S. Department of Agriculture, Albany, California 94710.
Mol Cell Biol. 1992 Dec;12(12):5301-10. doi: 10.1128/mcb.12.12.5301-5310.1992.
Phytochelatins (PCs) are metal-chelating peptides produced in plants and some fungi in response to heavy metal exposure. A Cd-sensitive mutant of the fission yeast Schizosaccharomyces pombe, defective in production of a PC-Cd-sulfide complex essential for metal tolerance, was found to harbor mutations in specific genes of the purine biosynthetic pathway. Genetic analysis of the link between metal complex accumulation and purine biosynthesis enzymes revealed that genetic lesions blocking two segments of the pathway, before and after the IMP branchpoint, are required to produce the Cd-sensitive phenotype. The biochemical functions of these two segments of the pathway are similar, and a model based on the alternate use of a sulfur analog substrate is presented. The novel participation of purine biosynthesis enzymes in the conversion of the PC-Cd complex to the PC-Cd-sulfide complex in the fission yeast raises an intriguing possibility that these same enzymes might have a role in sulfur metabolism in the fission yeast S. pombe, and perhaps in other biological systems.
植物螯合肽（PCs）是植物和一些真菌在接触重金属时产生的金属螯合肽。在粟酒裂殖酵母的一个镉敏感突变体中，发现其在产生对金属耐受性至关重要的PC - Cd - 硫化物复合物方面存在缺陷，该突变体在嘌呤生物合成途径的特定基因中存在突变。对金属复合物积累与嘌呤生物合成酶之间联系的遗传分析表明，阻断该途径在肌苷一磷酸（IMP）分支点之前和之后的两个片段的基因损伤是产生镉敏感表型所必需的。该途径这两个片段的生化功能相似，并提出了一个基于硫类似物底物交替使用的模型。嘌呤生物合成酶在裂殖酵母中将PC - Cd复合物转化为PC - Cd - 硫化物复合物中的新参与，引发了一种有趣的可能性，即这些相同的酶可能在粟酒裂殖酵母的硫代谢中发挥作用，也许在其他生物系统中也如此。
