Likó Z, Botyánszki J, Bódi J, Vass E, Majer Z, Hollósi M, Süli-Vargha H
Research Group for Peptide Chemistry, Hungarian Academy of Sciences, Budapest, Hungary.
Biochem Biophys Res Commun. 1996 Oct 14;227(2):351-9. doi: 10.1006/bbrc.1996.1512.
To investigate the role of secondary structure in the substrate specificity of human 72 kDa type IV collagenase, we synthesised linear and cyclic collagen sequence analogs. As Ca2+ plays a crucial role in the enzyme activity, the CD and FTIR spectra of the peptides were also measured in the presence of Ca2+. Most of the linear, but none of the cyclic peptides form stable 1:1 Ca2+ complexes. The cyclic hexapeptides adopt significantly different backbone conformations comprising not only beta-turns but also the less frequent gamma-turns. Consequently, in the cyclopeptides the scissile Gly-Ile(Leu) bond is embedded into a different conformational environment, but in spite of that none of them is a substrate or an inhibitor of the enzyme. The best substrate Ac-Pro-Leu-Gly-Leu-Ala-Gly-D-Lys-OH binds Ca2+, but does not form a stable 1:1 Ca2+ complex, which suggests that instead of a folded structure an extended flexible conformation is preferred by the enzyme.
为了研究二级结构在人72 kDa IV型胶原酶底物特异性中的作用，我们合成了线性和环状胶原序列类似物。由于Ca2+在酶活性中起关键作用，还在有Ca2+存在的情况下测量了肽的圆二色光谱（CD）和傅里叶变换红外光谱（FTIR）。大多数线性肽，但没有一个环状肽形成稳定的1:1 Ca2+复合物。环状六肽采用显著不同的主链构象，不仅包括β-转角，还包括较少出现的γ-转角。因此，在环肽中，可裂解的甘氨酸-异亮氨酸（亮氨酸）键嵌入不同的构象环境中，但尽管如此，它们都不是该酶的底物或抑制剂。最佳底物Ac-Pro-Leu-Gly-Leu-Ala-Gly-D-Lys-OH结合Ca2+，但不形成稳定的1:1 Ca2+复合物，这表明该酶更喜欢伸展的柔性构象而非折叠结构。
