Violand B N, Schlittler M R, Toren P C, Siegel N R
Animal Sciences Division, Monsanto Company, St. Louis, Missouri 63198.
J Protein Chem. 1990 Feb;9(1):109-17. doi: 10.1007/BF01024992.
Asparagine 99 in bovine (BST) and porcine somatotropins (PST) was converted to an isoaspartate residue during incubation at neutral or alkaline pH. Isoaspartate 99 BST or isoaspartate 99 PST was resolved from the normal somatotropin by reversed-phase high-performance liquid chromatography (HPLC). The altered peptide of residues 96-108 which contains isoaspartate 99 was detected by tryptic peptide mapping of the modified BST or PST. Amino acid sequencing, amino acid analysis, mass spectrometry, and co-elution with a chemically synthesized peptide containing isoaspartate 99 were used to demonstrate the existence of isoaspartate in the modified peptides. Peptide bond cleavage between Asn 99 and Ser 100 also occurred during incubation of BST and PST at neutral or alkaline pH. This chemically cleaved product was resolved on reversed-phase HPLC from both the isoaspartate 99 and normal somatotropin molecules.
牛生长激素（BST）和猪生长激素（PST）中的天冬酰胺99在中性或碱性pH条件下孵育时会转变为异天冬氨酸残基。通过反相高效液相色谱（HPLC）从正常生长激素中分离出异天冬氨酸99的BST或异天冬氨酸99的PST。通过对修饰的BST或PST进行胰蛋白酶肽图谱分析，检测到含有异天冬氨酸99的96 - 108位残基的改变肽段。氨基酸测序、氨基酸分析、质谱分析以及与含有异天冬氨酸99的化学合成肽共洗脱，用于证明修饰肽中存在异天冬氨酸。在BST和PST于中性或碱性pH条件下孵育期间，天冬酰胺99和丝氨酸100之间的肽键也会发生断裂。这种化学裂解产物通过反相HPLC从异天冬氨酸99和正常生长激素分子中分离出来。
