Cynis Holger, Schilling Stephan, Bodnár Mandy, Hoffmann Torsten, Heiser Ulrich, Saido Takaomi C, Demuth Hans-Ulrich
Probiodrug AG, Weinbergweg 22, 06120 Halle/Saale, Germany.
Biochim Biophys Acta. 2006 Oct;1764(10):1618-25. doi: 10.1016/j.bbapap.2006.08.003. Epub 2006 Aug 16.
Mammalian cell lines were examined concerning their Glutaminyl Cyclase (QC) activity using a HPLC method. The enzyme activity was suppressed by a QC specific inhibitor in all homogenates. Aim of the study was to prove whether inhibition of QC modifies the posttranslational maturation of N-glutamine and N-glutamate peptide substrates. Therefore, the impact of QC-inhibition on amino-terminal pyroglutamate (pGlu) formation of the modified amyloid peptides Abeta(N3E-42) and Abeta(N3Q-42) was investigated. These amyloid-beta peptides were expressed as fusion proteins with either the pre-pro sequence of TRH, to be released by a prohormone convertase, or as engineered amyloid precursor protein for subsequent liberation of Abeta(N3Q-42) after beta- and gamma-secretase cleavage during posttranslational processing. Inhibition of QC leads in both expression systems to significantly reduced pGlu-formation of differently processed Abeta-peptides. This reveals the importance of QC-activity during cellular maturation of pGlu-containing peptides. Thus, QC-inhibition should impact bioactivity, stability or even toxicity of pyroglutamyl peptides preventing glutamine and glutamate cyclization.
采用高效液相色谱法检测了哺乳动物细胞系的谷氨酰胺环化酶（QC）活性。在所有匀浆中，该酶活性均被QC特异性抑制剂所抑制。本研究的目的是证明抑制QC是否会改变N - 谷氨酰胺和N - 谷氨酸肽底物的翻译后成熟过程。因此，研究了QC抑制对修饰的淀粉样肽Abeta(N3E - 42)和Abeta(N3Q - 42)氨基末端焦谷氨酸（pGlu）形成的影响。这些淀粉样β肽表达为与促甲状腺激素释放激素（TRH）的前原序列融合的蛋白，由激素原转化酶释放，或者表达为工程化淀粉样前体蛋白，以便在翻译后加工过程中经β和γ分泌酶切割后随后释放Abeta(N3Q - 42)。在两种表达系统中，抑制QC均导致不同加工的Abeta肽的pGlu形成显著减少。这揭示了QC活性在含pGlu肽的细胞成熟过程中的重要性。因此，抑制QC应会影响焦谷氨酰肽的生物活性、稳定性甚至毒性，从而阻止谷氨酰胺和谷氨酸环化。
