SIMULTANEOUS RACEMIZATION AND ISOMERIZATION AT SPECIFIC ASPARTIC-ACID RESIDUES IN ALPHA-B-CRYSTALLIN FROM THE AGED HUMAN LENS
SIMULTANEOUS RACEMIZATION AND ISOMERIZATION AT SPECIFIC ASPARTIC-ACID RESIDUES IN ALPHA-B-CRYSTALLIN FROM THE AGED HUMAN LENS
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DOI：
10.1016/0167-4838(94)90003-5
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发表时间：
1994-02-16
期刊：
影响因子：
--
通讯作者：
HARADA, K
中科院分区：
文献类型：
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作者：
FUJII, N;ISHIBASHI, Y;HARADA, K
我们提供的证据表明，消旋化和异构化的乙酰（天冬氨酸）残基同时发生在α B-晶状体蛋白在透镜的老年人（平均年龄：80岁）和年轻人（年龄：II个月）。我们纯化了α B-晶状体蛋白并将其进行胰蛋白酶消化。所得肽通过反相高效色谱法（RP-HPLC）分离，并通过氨基酸组成，序列分析和质谱进行了表征。在老化的α B-晶状体蛋白的13个Asp/天冬酰胺基（Asn）残基中，发现两个特异性位点，Asp-36（D/L：0.92）和Asp-62（D / L：0.57），被高度外消旋化和异构化以形成β-Asp残基。通过RP-HPLC，含β-Asp的肽与含正常Asp的（α-Asp）肽明显区分开。在老化的α B-晶状体蛋白中，Asp残基的外消旋化和异构化可能通过琥珀酰亚胺中间体发生。在年轻的α B-晶体蛋白，我们既没有观察到消旋化，也没有异构化。我们还发现，Met-68被氧化，形成Met亚砜在更大程度上在老年α B-晶体蛋白比年轻的α B-晶体蛋白。我们得出结论，外消旋化，异构化和氧化的α B-晶状体蛋白自发发生在老化过程中。
We provide evidence that the racemization and isomerization of aspartyl(Asp) residues occur simultaneously in the alpha B-crystallin in the lens of aged (mean age: 80 years) and young (age: II months) humans. We purified alpha B-crystallin and subjected it to tryptic digestion. The resulting peptides were separated by reverse-phase high-performance chromatography (RP-HPLC) and were characterized by amino-acid composition, sequence analysis and mass spectrometry. Two specific sites, Asp-36 (D / L of Asp: 0.92) and Asp-62(D / L of Asp: 0.57), among 13 Asp/ asparginyl (Asn) residues in aged alpha B-crystallin, were found to be highly racemized and isomerized to form beta-Asp residues. The beta-Asp-containing peptides were clearly distinguished from normal Asp-containing (alpha-Asp) peptides by RP-HPLC. The racemization and isomerization of Asp residues in aged alpha B-crystallin may occur via a succinimide intermediate. In young alpha B-crystallin, we observed neither racemization nor isomerization. We also found that Met-68 was oxidized to form Met sulfoxide to a greater extent in aged alpha B-crystallin than in young alpha B-crystallin. We concluded that racemization, isomerization, and oxidation of alpha B-crystallin occur spontaneously in the aging process.