Kaji Y, Oshika T, Okamoto F, Fujii N
Department of Ophthalmology, Tsukuba University Institute of Clinical Medicine, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8565, Japan.
Br J Ophthalmol. 2009 Jul;93(7):974-6. doi: 10.1136/bjo.2007.135889. Epub 2009 Mar 9.
D-beta-aspartic acid residues, which are biologically uncommon, have been reported to accumulate in various proteins of the living body with age. In the present study, D-beta-aspartic acid-containing proteins were found to be localised in pingueculae, which represent one of the most prominent age-related ocular changes.
Surgical specimens of conjunctivae with or without pingueculae were obtained from eight patients. Immunohistochemical localisation of D-beta-aspartic acid-containing proteins was performed using a polyclonal antibody against D-beta-aspartic acid-containing peptides.
Strong immunoreactivity to D-beta-aspartic acid-containing peptides was detected in the subepithelial amorphous materials of all surgical specimens with pingueculae. In contrast, no immunoreactivity to D-beta-aspartic acid-containing peptides was detected in the specimens without pingueculae.
Pingueculae are thought to be aggregates of proteins that contain D-beta-aspartic acid residues. It is known that the conversion of L- to D-aspartyl residues is accelerated by ultraviolet irradiation. In addition, D-beta-aspartic acid-containing proteins, in general, tend to aggregate with each other and accumulate in the tissues. These facts indicate that ultraviolet irradiation-induced racemisation of aspartic acid is closely related to the development of pingueculae.
D-β-天冬氨酸残基在生物学上并不常见，据报道，随着年龄增长，其会在生物体内的各种蛋白质中积累。在本研究中，发现含D-β-天冬氨酸的蛋白质定位于睑裂斑，睑裂斑是与年龄相关的最显著眼部变化之一。
从8名患者身上获取有或没有睑裂斑的结膜手术标本。使用针对含D-β-天冬氨酸肽的多克隆抗体进行含D-β-天冬氨酸蛋白质的免疫组织化学定位。
在所有有睑裂斑的手术标本的上皮下无定形物质中检测到对含D-β-天冬氨酸肽的强免疫反应性。相比之下，在没有睑裂斑的标本中未检测到对含D-β-天冬氨酸肽的免疫反应性。
睑裂斑被认为是含有D-β-天冬氨酸残基的蛋白质聚集体。已知紫外线照射会加速L-天冬氨酰残基向D-天冬氨酰残基的转化。此外，一般来说，含D-β-天冬氨酸的蛋白质倾向于相互聚集并在组织中积累。这些事实表明，紫外线照射诱导的天冬氨酸消旋化与睑裂斑的形成密切相关。
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