Lee Thomas N, Alborn William E, Knierman Michael D, Konrad Robert J
Eli Lilly and Company, Indianapolis, IN 46285, USA.
Biochem Biophys Res Commun. 2006 Dec 1;350(4):1038-43. doi: 10.1016/j.bbrc.2006.09.155. Epub 2006 Oct 6.
We have previously shown that streptozotocin (STZ) inhibits O-GlcNAc-selective N-acetyl-beta-d-glucosaminidase (O-GlcNAcase), the enzyme that removes O-GlcNAc from proteins. In light of this observation, we explored the possibility that the diabetogenic toxin alloxan, an O-GlcNAc transferase (OGT) inhibitor, might also inhibit O-GlcNAcase. Alloxan inhibited islet O-GlcNAcase with a dose-response much like that of STZ. Similar to STZ, islet O-GlcNAcase was more susceptible to alloxan inhibition than was brain O-GlcNAcase. Alloxan directly inhibited recombinant O-GlcNAcase activity with a dose-response very similar to that of STZ. Subsequent LC/MS/MS analysis revealed that alloxan modified the tryptic digest pattern of the enzyme. One tryptic peptide LGCFEIAK(894-901) was modified by alloxan. Two other tryptic peptides, LDQVSQFGCR(158-167) and SFALLFDDIDHNMCAADK(168-185), both N-terminal active site peptides, were absent after alloxan treatment. Together, these data demonstrate that alloxan is an inhibitor of O-GlcNAc-selective N-acetyl-beta-d-glucosaminidase, with inhibition corresponding to an altered tryptic digest pattern of N-terminal active site peptides.
我们之前已经表明，链脲佐菌素（STZ）可抑制O-GlcNAc选择性N-乙酰-β-D-氨基葡萄糖苷酶（O-GlcNAcase），该酶负责从蛋白质上去除O-GlcNAc。鉴于这一观察结果，我们探讨了致糖尿病毒素四氧嘧啶（一种O-GlcNAc转移酶（OGT）抑制剂）是否也可能抑制O-GlcNAcase的可能性。四氧嘧啶抑制胰岛O-GlcNAcase的剂量反应与STZ非常相似。与STZ类似，胰岛O-GlcNAcase比脑O-GlcNAcase更容易受到四氧嘧啶的抑制。四氧嘧啶直接抑制重组O-GlcNAcase的活性，其剂量反应与STZ非常相似。随后的液相色谱/串联质谱（LC/MS/MS）分析表明，四氧嘧啶改变了该酶的胰蛋白酶消化模式。一个胰蛋白酶肽段LGCFEIAK(894 - 901)被四氧嘧啶修饰。另外两个胰蛋白酶肽段，LDQVSQFGCR(158 - 167)和SFALLFDDIDHNMCAADK(168 - 185)，这两个都是N端活性位点肽段，在四氧嘧啶处理后消失。总之，这些数据表明四氧嘧啶是O-GlcNAc选择性N-乙酰-β-D-氨基葡萄糖苷酶的抑制剂，其抑制作用与N端活性位点肽段的胰蛋白酶消化模式改变相对应。
