School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, Geneva, Switzerland.
Eur J Pharm Biopharm. 2013 Sep;85(1):42-52. doi: 10.1016/j.ejpb.2013.03.015.
Oxidation of methionine (Met) residues is one of the major chemical degradations of therapeutic proteins. This chemical degradation can occur at various stages during production and storage of a biotherapeutic drug. During the oxidation process, the side chain of methionine residue undergoes a chemical modification, with the thioether group substituted by a sulfoxide group. In previous papers, we showed that oxidation of the two most accessible methionine residues of recombinant human growth hormone (r-hGH), Met¹⁴ and Met¹²⁵, has no influence on the conformation of the protein [1]. However, the oxidized r-hGH is less thermally stable than the native protein [2]. In the current work, the consequences of the oxidation of these two methionine residues on the aggregation of r-hGH were investigated. The aggregation properties and kinetics of the native and oxidized r-hGH were measured in different buffers with both spectroscopic and chromatographic methods. Stabilities of oxidized and non-oxidized r-hGH were studied after storage at 37°C and freeze/thawing cycles. Methionine oxidation influenced the aggregation properties of r-hGH. In accelerated stability studies at 37°C, oxidized hormone aggregated more and faster than non-oxidized hormone. In freezing/thawing stability studies, it was found that oxidized r-hGH was less stable than its non-oxidized counterpart. In case of hGH, we have shown that chemical degradations such as oxidation can affect its physical stability and can induce aggregation.
蛋氨酸（Met）残基的氧化是治疗性蛋白质的主要化学降解之一。这种化学降解可能发生在生物治疗药物生产和储存的各个阶段。在氧化过程中，蛋氨酸残基的侧链发生化学修饰，硫醚基团被亚砜基团取代。在以前的论文中，我们表明重组人生长激素（r-hGH）的两个最易接近的蛋氨酸残基 Met¹⁴和 Met¹²⁵的氧化对蛋白质的构象没有影响[1]。然而，氧化的 r-hGH 的热稳定性不如天然蛋白质[2]。在当前的工作中，研究了这两个蛋氨酸残基的氧化对 r-hGH 聚集的影响。使用光谱和色谱方法，在不同的缓冲液中测量了天然和氧化的 r-hGH 的聚集特性和动力学。研究了在 37°C 下储存和反复冻融后氧化和非氧化 r-hGH 的稳定性。蛋氨酸氧化影响 r-hGH 的聚集特性。在 37°C 的加速稳定性研究中，氧化激素比非氧化激素聚集得更多、更快。在反复冻融稳定性研究中，发现氧化的 r-hGH 不如非氧化的 r-hGH 稳定。对于 hGH，我们已经表明，化学降解，如氧化，会影响其物理稳定性并诱导聚集。
