Tou Jacob S, Violand Bernard N, Chen Zi Yi, Carroll James A, Schlittler Michael R, Egodage Kamal, Poruthoor Simon, Lipartito Carol, Basler Darrell A, Cagney Judy W, Storrs S Bradley
Global Chemistry R&D, Monsanto, 800 N. Lindbergh Blvd, St. Louis, MO 63167, USA.
Protein J. 2009 Feb;28(2):87-95. doi: 10.1007/s10930-009-9167-2.
Under stressed conditions such as prolonged exposure to high pH, the C-terminal disulfide bridge in bovine somatotropin (bST) is susceptible to a base catalyzed beta-elimination reaction. This reaction converts the disulfide bond to a dehydroalanine residue with loss of a sulphur atom. Two altered species were isolated in pure form and determined to be generated from this dehydroalanine intermediate. One is a monomeric lanthionyl bST (L-bST) with a thioether linkage, and the other is an inter-molecular disulfide linked dimer containing a lysinoalanine. These two novel structures were unambiguously determined using various techniques including enzymatic digestion, amino acid sequencing and analysis, and mass spectrometry. The monomeric L-bST was demonstrated to be equipotent to normal bST in a hypox rat assay, thus showing that formation of lanthionine in place of this disulfide bond does not affect it bioactivity.
在诸如长时间暴露于高pH值等应激条件下，牛生长激素（bST）的C末端二硫键易受碱催化的β-消除反应影响。该反应将二硫键转化为脱氢丙氨酸残基，同时损失一个硫原子。两种变体以纯形式分离出来，并确定是由该脱氢丙氨酸中间体产生的。一种是具有硫醚键的单体羊毛硫氨酸化bST（L-bST），另一种是含有赖氨酸丙氨酸的分子间二硫键连接的二聚体。使用包括酶切、氨基酸测序与分析以及质谱分析等多种技术明确确定了这两种新结构。在低氧大鼠试验中，单体L-bST被证明与正常bST具有同等效力，因此表明用羊毛硫氨酸取代该二硫键的形成不会影响其生物活性。
