Violand B N, Schlittler M R, Kolodziej E W, Toren P C, Cabonce M A, Siegel N R, Duffin K L, Zobel J F, Smith C E, Tou J S
Animal Sciences Division, Monsanto Company, St. Louis, Missouri 63198.
Protein Sci. 1992 Dec;1(12):1634-41. doi: 10.1002/pro.5560011211.
Aspartate129 in porcine somatotropin was converted into a cyclic imide residue (succinimide) under acidic solution conditions. Reversed-phase high performance liquid chromatography was utilized to isolate and quantitate this altered species, which accounted for approximately 30% of the total protein. The molecular mass of this modified species was determined by electrospray mass spectrometry to be 18 Da less than normal porcine somatotropin, indicative of a loss of 1 H2O molecule. Tryptic peptide mapping demonstrated that the peptide composed of residues 126-133 was altered in this modified protein. Amino acid analysis, amino acid sequencing, mass spectrometry, and capillary zone electrophoresis were used to demonstrate that aspartate129 in this peptide had been converted into a succinimide residue. Further confirmation that this peptide contained a succinimide was obtained by hydrolyzing the modified peptide at pH 9.0, which yielded both the aspartate and isoaspartate peptides.
在酸性溶液条件下，猪生长激素中的天冬氨酸129被转化为环状酰亚胺残基（琥珀酰亚胺）。利用反相高效液相色谱法分离并定量这种变化的物种，其约占总蛋白的30%。通过电喷雾质谱法测定这种修饰物种的分子量比正常猪生长激素少18 Da，表明失去了1个水分子。胰蛋白酶肽图谱显示，由残基126 - 133组成的肽在这种修饰蛋白中发生了变化。氨基酸分析、氨基酸测序、质谱法和毛细管区带电泳用于证明该肽中的天冬氨酸129已转化为琥珀酰亚胺残基。通过在pH 9.0条件下水解修饰肽得到天冬氨酸肽和异天冬氨酸肽，进一步证实该肽含有琥珀酰亚胺。
