Ornithine decarboxylase encoded by chlorella virus PBCV-1.
Ornithine decarboxylase encoded by chlorella virus PBCV-1.
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DOI：
10.1006/viro.2002.1573
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发表时间：
2002-09
期刊：
影响因子：
3.7
通讯作者：
Tiara A Morehead;J. Gurnon;B. Adams;K. Nickerson;Lisa A. Fitzgerald;J. V. Van Etten
中科院分区：
文献类型：
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作者：
Tiara A Morehead;J. Gurnon;B. Adams;K. Nickerson;Lisa A. Fitzgerald;J. V. Van Etten
对小球藻病毒PBCV-1的330-kb基因组进行序列分析，发现了一个开放阅读框A207 R，该框编码的蛋白与许多真核生物的鸟氨酸脱羧酶（ODC）具有37-41%的氨基酸同一性。克隆了a207 r基因，并在大肠杆菌中表达了His-A207 R融合蛋白。该重组蛋白催化鸟氨酸的吡哆醛5 '-磷酸依赖性脱羧为腐胺，这是多胺生物合成途径中的第一步。该酶的最适pH值为9.0，最适温度为42 ℃，并且它需要二硫苏糖醇以获得最大活性。该酶对鸟氨酸的K（m）为0.78 mM，比活性为100 μ mol/min/mg蛋白质。PBCV-1 ODC对竞争性抑制剂L-精氨酸和不可逆抑制剂二氟甲基精氨酸非常敏感，但对不可逆抑制剂二氟甲基鸟氨酸不太敏感。a207 r基因在PBCV-1感染的早期和晚期都有表达，并且在沙门氏菌病毒中高度保守。42-kDa PBCV-1 ODC（372个氨基酸）是数据库中最小的ODC，据我们所知，是第一个病毒编码的ODC。
Sequence analysis of the 330-kb genome of chlorella virus PBCV-1 revealed an open reading frame, A207R, which encodes a protein with 37-41% amino acid identity to ornithine decarboxylase (ODC) from many eukaryotic organisms. The a207r gene was cloned and the protein was expressed as a His-A207R fusion protein in Escherichia coli. The recombinant protein catalyzes pyridoxal 5'-phosphate-dependent decarboxylation of ornithine to putrescine, the first step in the polyamine biosynthetic pathway. The enzyme has a pH optimum of 9.0 and a temperature optimum of 42 degrees C, and it requires dithiothreitol for maximal activity. The enzyme has a K(m) for ornithine of 0.78 mM and a specific activity of 100 micromol/min/mg protein. PBCV-1 ODC is quite sensitive to the competitive inhibitor L-arginine and the irreversible inhibitor difluoromethylarginine but it is less sensitive to the irreversible inhibitor difluoromethylornithine. The a207r gene is expressed both early and late in PBCV-1 infection and is highly conserved among the chlorella viruses. The 42-kDa PBCV-1 ODC (372 amino acids) is the smallest ODC in the databases and, to our knowledge, is the first virus-encoded ODC.