Characterization of phytochelatin synthase produced by the primitive red alga Cyanidioschyzon merolae.
Characterization of phytochelatin synthase produced by the primitive red alga Cyanidioschyzon merolae.
复制标题
原始红藻 Cyanidioschyzon merolae 产生的植物螯合素合酶的表征。
作者：
Y. Osaki;Tomoo Shirabe;H. Nakanishi;T. Wakagi;E. Yoshimura
植物螯合素（Phytochelatins，PC）是一类非蛋白质多肽，其结构为[（γ-Glu-Cys）n-Gly（n≥ 2）]，主要在高等植物中参与重金属的解毒作用。肽的合成是由植物螯合素合成酶（PCS）介导的，它被一系列重金属激活。分离了原始红藻Cyanidioschyzon merolae基因组DNA中发现的PCS样基因CmPCS，并产生了与CmPCS N末端六聚组氨酸标签融合的重组蛋白（rCmPCS）。该蛋白质以金属依赖性方式介导谷胱甘肽合成PC的发现清楚地表明rCmPCS具有功能性。在50 °C的反应温度下获得最大活性，该温度显著高于从高等植物瓜形蝇子草分离的PCS的最大活性所需的温度，这可能是由于该菌是嗜热菌。CmPCS表现出最佳的pH值在一个稍高的区域比更高的植物PCS，可能是由于在催化三元组中的有效性较低的电荷中继网络。此外，由金属离子激活的酶的模式是特定的rCmPCS，与Ag+，Cu 2+，Hg 2+仅显示有限的激活。与其他真核生物PCS相比，CmPCS在N-末端区域从残基1至109具有额外的结构域，并且在C-末端结构域中含有较少的半胱氨酸残基。这些差异可能是CmPCS激活的金属特异性的原因。虽然酶制剂在4 °C下储存时逐渐丧失PCS活性，但制剂中包含Cd 2+有效地防止了活性的降低。此外，Cd 2+有效地恢复了失活酶的活性。这些结果表明，镉离子结合酶，以保持肽的结构完整性。
Phytochelatins (PCs), non-protein peptides with the general structure [(γ-Glu-Cys)n-Gly (n≥ 2)], are involved in the detoxification of toxic heavy metals mainly in higher plants. The synthesis of the peptides is mediated by phytochelatin synthase (PCS), which is activated by a range of heavy metals. CmPCS, a PCS-like gene found in the genomic DNA of the primitive red alga Cyanidioschyzon merolae, was isolated and a recombinant protein (rCmPCS) fused with a hexahistidine tag at the N-terminus of CmPCS was produced. The finding that this protein mediated PC synthesis from glutathione in a metal-dependent way clearly establishes that rCmPCS is functional. The maximum activity was attained at a reaction temperature of 50 °C, considerably higher than the temperature required for the maximal activity of PCS isolated from the higher plant Silene cucubalus, probably due to the alga being a thermophile. CmPCS showed optimal pH in a slightly higher region than higher plant PCSs, probably due to the less effective charge relay network in the catalytic triad. In addition, the pattern of enzyme activation by metal ions was specific to rCmPCS, with Ag+, Cu2+, and Hg2+ showing only limited activation. In contrast to other eukaryotic PCSs, CmPCS has an extra domain in the N-terminal region from residues 1 to 109, and contains fewer cysteine residues in the C-terminal domain. These differences may be responsible for the metal specificity of the activation of CmPCS. Although the enzyme preparation lost PCS activity progressively when stored at 4 °C, the inclusion of Cd2+ in the preparation effectively prevented the reduction of activity. Furthermore, Cd2+ effectively restored the activity of the inactivated enzyme. These results indicate that Cd2+ ions bind the enzyme to maintain the structural integrity of the peptides.
DOI：
10.1046/j.1432-1327.2001.02293.x
发表时间：
2001-07-01
期刊：
EUROPEAN JOURNAL OF BIOCHEMISTRY
影响因子：
--
作者：
Clemens, S;Schroeder, JI;Degenkolb, T
通讯作者：
Degenkolb, T
粟酒裂殖酵母γ-谷氨酰铜结合肽的研究。
DOI：
--
发表时间：
1988
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Reese,RN;Mehra,RK;Tarbet,EB;Winge,DR
通讯作者：
Winge,DR