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2024年2月9日發(作者：運動通訊稿)

生物化學與生物物理進展

Progress in Biochemistry and Biophysics

發布日期：（編輯部填寫）

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補充材料二

Supplementary data 2

病理性α-SYN的化學修飾形式的生物信息學數據分析

An Analysis of Bioinformatics Datats Related to Chemical Modification Forms of

Pathological α-SYN

i．在DLB病人LBs內，α-SYN的磷酸化修飾率達90%（而在正常腦內，生理性α-SYN的磷酸化修飾[1]率僅4%）．α-SYN的絲氨酸殘基-87（Ser-87）、Ser-125和Ser-129是主要的磷酸化修飾位點，而且Ser-129位點的磷酸化修飾水平最高[2]．蛋白質磷酸化修飾有助于穩定α-SYN的β-片層[3]．蛋白質磷酸化修飾促進α-SYN進行纖維化聚集[3]．

ii．在PD病人LBs內，α-SYN的氧化修飾水平不低于它的磷酸化修飾水平[3]．首先，α-SYN的酪氨酸殘基-39（Tyr-39）、Tyr-125、Tyr-133和Tyr-136是一組氧化修飾位點，氧化修飾方式是硝基化和羥基氧化[2]．硝基化將弱極性的Tyr轉變為強極性的3-硝基酪氨酸，α-SYN由此不能形成穩定的β-片層；羥基氧化，5]將兩個Tyr轉變為一個Tyr同二聚體，α-SYN借此形成分子內、間交聯物[4Met轉變為剛性和極性均較強的亞砜和砜，從而弱化了α-SYN的β-片層[6結合于α-SYN[2，3，8]．其次，α-SYN的蛋氨酸殘基-1（Met-1）、Met-5、Met-116和Met-127是另外一組氧化修飾位點，氧化方式是巰基氧化[2]．巰基氧化將，7]．再次，DA及其氧化代謝物（包括超氧陰離子、過氧化氫等過氧化物以及多巴醌、5,6-二羥基吲哚、5,6-吲哚醌等DA衍生物）廣泛地共價．這種非特異性氧化修飾方式干擾DA及其氧化代謝物在生理狀態下特異地非共價結合于α-SYN，并且進一步干擾α-SYN形成β-片層[9-11]．蛋白質氧化修飾促進α-SYN進行非纖維化聚集[2]．

iii．在PD病人LBs內，Ub通過賴氨酸殘基-63（Lys-63）共價結合于α-SYN的2個泛素化修飾位點，即，Lys-10和Lys-12[2]．Ub與α-SYN一樣也是LBs的特征蛋白質成分[8]．Ub在LBs內的存在形式是Ub單體、2分子Ub單位（一個Ub的C末端甘氨酸殘基的羧基與另外一個Ub的Lys-48的ε-氨基通過異肽鍵形成的二肽）乃至多分子Ub單位（或Ub鏈）．蛋白質泛素化修飾促進α-SYN進行纖維化聚集[12]．在DLB病人LBs內，Ub樣蛋白質修飾物（Ub-like protein modifiers，ULMs）異構體SUMO1（small Ub-like modifier

1）以類泛素化（sumoylation）修飾方式結合于α-SYN的N端某個Lys-（可能是Lys-102）[13]；在PD病人LBs內，ULMs異構體NEDD8（neural precursor cell-expresd, developmentally down-regulated protein）以同樣方式結合于α-SYN的相同氨基酸殘基位點[13]．蛋白質類泛素化修飾促進α-SYN進行纖維化聚集[2Asp-119、Tyr-133或Asp-135位點被物質代謝產生的自由基有選擇地截斷[2α-SYN進行纖維化聚集[2]．

v．在PD病人和DLB病人LBs內，α-SYN通過酶促催化反應形成分子內、間交聯物[14]．可溶性組織，3]，3]．

iv．在DLB病人LBs內，α-SYN在天冬氨酸殘基-115（Asp-115）、天冬酰胺殘基-122（Asn-122）、．分子斷裂使α-SYN失去了C端部分氨基酸序列，α-SYN由此減弱了分子伴侶活性和蛋白質結合作用．這種蛋白質化學修飾形式促進

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生物化學與生物物理進展 Prog. Biochem. Biophys.

型轉谷氨酰胺酶（soluble tissue transglutamina，tTGa）催化谷氨酰胺（Gln）與Lys之間的轉酰胺基反應[2]．在α-SYN內部和（或）α-SYN分子之間，tTGa催化Gln-79或Gln-109與N端區段一些Lys-（Lys-，8，14]的具體位置不清楚）之間以及Gln-79、Gln-99或Gln-109與Lys-60之間的轉酰胺基反應，α-SYN借此形成分子內、間交聯物[3]．在LBD病人LBs內，α-SYN通過非酶促催化反應形成分子內、間交聯物[2．葡萄糖代謝和脂質過氧化產生的高反應性醛類物質通過自由基誘導的氧化還原反應廣泛地在蛋白質Lys-位點形成高級糖基化終末產物（advanced glycation end-products，AGEs），AGEs之間相互作用使蛋白質形成交聯物[2]．α-SYN極有可能通過上述非酶促催化反應在它的15個Lys-位點形成分子內、間交聯物．蛋白質交聯阻礙α-SYN形成完整的四級結構[2]．這種蛋白質化學修飾形式促進α-SYN進行非纖維化聚集[15-17]．

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