CD-113 FOURIER-TRANSFORM NUCLEAR MAGNETIC-RESONANCE OF CADMIUM(II) CARBONIC-ANHYDRASES AND CADMIUM(II) ALKALINE-PHOSPHATASE
CD-113 FOURIER-TRANSFORM NUCLEAR MAGNETIC-RESONANCE OF CADMIUM(II) CARBONIC-ANHYDRASES AND CADMIUM(II) ALKALINE-PHOSPHATASE
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DOI：
10.1021/ja00434a058
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发表时间：
1976-01-01
影响因子：
15
通讯作者：
COLEMAN, JE
中科院分区：
文献类型：
--
作者：
ARMITAGE, IM;PAJER, RT;COLEMAN, JE
2b金属Zn（II）在保持多种金属酶的催化活性形式方面的基本性质是确定的。1· 2通过研究含有化学上相似的2b族金属离子的天然蛋白质或类似物，阐明金属离子结合位点的结构和金属在酶作用机制中的功能作用（Cd（II），Hg（II））在Zn（II）位点上的结合受到这些离子的固有性质的限制（填充的d壳）使得它们作为光谱探针的价值很小。因此，尽管在优选的配位几何形状和易变性的配体场诱导的结构扭曲的差异，酶结合的金属的特性已在很大程度上推断从光谱性质的酶，其中过渡金属离子已被取代的天然Zn（II）离子。1最近关于FT-NMR应用于各种无机盐和小模型络合物中的金属核素的报道3· 4表明，这种技术可能适合于直接观察结合在酶微环境中的天然金属的抗磁性类似物。在本研究中，~（113）Cd核具有自旋，对核磁共振检测的灵敏度高于~（67）Z。n是合理的第一候选者。对屏蔽常数的大的顺磁贡献导致化学位移的大的变化，其与金属离子的键合性质的变化反映在对于常见的镉化合物的> 640 ppm的化学位移范围内。3这一事实加上其对取代基效应的极端敏感性和对弛豫机制的大偶极贡献使113 Cd成为理想的NMR探针。本文报道了用~（113）Cd（Ⅱ）离子取代金属酶牛碳酸酐酶B（BCA B）、人碳酸酐酶B（HCA B）和大肠杆菌碱性磷酸酶的Zn（Ⅱ）离子的FT-NMR共振谱的观察结果和特征。大肠杆菌（AP）FBCAB和F1 CAB从牛和人红细胞获得。6从E. coliCW3747。7.通过透析或透析从纯化的酶中除去锌。
The essential nature of the 2b metal Zn (II) in maintaining the catalytically active form of a wide variety of metalloen-zymes is well established. 1· 2 Elucidation of the structure of the metal ion binding site and the functional role of the metal (s) in the mechanism of enzyme action by study of the native protein or analogs containing the chemically similar group 2b metal ions (Cd (II), Hg (II)) bound at the Zn (II) site is limited by the intrinsic properties of these ions (filled d shell) making them of little value as spectroscopic probes. Thus, despite differences in preferred coordination geometry and suscepti-bility to ligand-field induced structural distortions, the characteristics of the enzyme-bound metal have been largely inferred from the spectral properties of the enzymes in which transition metal ions have been substituted for the native Zn (II) ion. 1 Recent reports on the application of FT-NMR to metal nuclides in a variety of inorganic salts and small model complexes3· 4 suggest that this technique may be suited to the direct observation of the diamagnetic analogue of the native metal bound in the microenvironment of enzymes. In this re-gard, the 113Cd nucleus with spin and its highersensitivity to NMR detection compared to 67Z. n is a reasonable first candidate. The large paramagnetic contribution to the shielding constant leads to large changes in the chemical shift with changes in the nature of bonding to the metal ion as re-flected in a chemical shift range of> 640 ppm for common compounds of cadmium. 3 This fact coupled with its extreme sensitivity to substituent effects and a large dipolar contribution to the relaxation mechanism make 1 l3Cd an ideal NMR probe. We wish to report on the observation and characteristics of the FT-NMR resonances of the 113Cd (II) ion substituted for the intrinsic Zn (II) ion (s) of the metalloenzymes, bovine carbonic anhydrase B (BCAB), human carbonic anhydrase B (HCAB), and alkaline phosphatase of E. coli (AP) F BCAB and F1CAB were obtained from bovine and human erythrocytes. 6 AP was isolated from E. coli CW3747. 7 Zinc was removed from the purified enzymes either by dialysis