Korpela T K, Himanen J P, Mattinen J, Mekhanik M L, Torchinskiĭ Iu M
Bioorg Khim. 1987 Apr;13(4):550-1.
31P NMR spectra of the cytosolic chicken aspartate aminotransferase have been recorded at 161.7 MHz in the pH range of 5.7 to 8.2. The 31P chemical shift was found to be pH-dependent with a pK of 6.85; difference in the chemical shift at pH 5.7 and 8.2 is only 0.35 ppm. The monoanion-dianion transition of 5'-phosphate group of a model Schiff base of pyridoxal phosphate with 2-aminobutanol in methanol is accompanied by a change in 31P chemical shift of 5.2 ppm. It is inferred that the phosphate group of the protein--bound coenzyme is in dianionic form throughout the investigated pH range; the small pH-dependent change of chemical shift may be due to a protein conformational change that affects O-P-O bond angle. In the presence of the 0.1 M succinate, 31P chemical shift of the enzyme remains constant in the pH range of 5.0 to 8.3.
已在161.7 MHz下记录了胞质鸡天冬氨酸转氨酶在pH 5.7至8.2范围内的31P NMR谱。发现31P化学位移与pH有关，pK为6.85；pH 5.7和8.2时化学位移的差异仅为0.35 ppm。磷酸吡哆醛与2-氨基丁醇在甲醇中的模型席夫碱的5'-磷酸基团的单阴离子-双阴离子转变伴随着31P化学位移5.2 ppm的变化。据推断，在整个研究的pH范围内，与蛋白质结合的辅酶的磷酸基团呈双阴离子形式；化学位移随pH的微小变化可能是由于影响O-P-O键角的蛋白质构象变化所致。在0.1 M琥珀酸盐存在下，酶的31P化学位移在pH 5.0至8.3范围内保持恒定。
