Alfaro-Lopez J, Yuan W, Phan B C, Kamath J, Lou Q, Lam K S, Hruby V J
Department of Chemistry, Arizona Cancer Center, University of Arizona, Tucson, Arizona 85721, USA.
J Med Chem. 1998 Jun 18;41(13):2252-60. doi: 10.1021/jm9707885.
On the basis of the efficient substrate for p60c-src protein tyrosine kinase (PTK) YIYGSFK-NH2 (1) (Km = 55 microM) obtained by combinatorial methods, we have designed and synthesized a series of conformationally and topographically constrained substrate-based peptide inhibitors of this enzyme, which showed IC50 values in the low-micromolar range (1-3 microM). A "rotamer scan" was performed by introducing the four stereoisomers of beta-Me(2')Nal in the postulated interaction site of the peptide inhibitor 23(IC50 = 1.6 microM). This substitution led to selective and potent inhibitors of p60c-src PTK; however, no substantial difference in potency was observed among them. This and the results of the "stereochemical scan" performed at residues 2 and 7 of 3 (peptides 19-21), which form the disulfide bond, may suggest that the enzyme active site does not have rigid topographic requirements and thus is able to achieve important conformational changes to bind the ligand as long as the pharmacophore pattern in the inhibitor is conserved. Two new potent iodo-containing nonphosphorylatable tyrosine analogues were also incorporated into our lead inhibitory sequence 23, producing the most potent inhibitors for p60c-src PTK identified thus far in our studies. Compounds 29 and 30 exhibit IC50 values of 0.13 and 0.54 microM, respectively. Peptide 29 is 420-fold more potent than the parent peptide 1. Selectivity studies of peptides 23-30 toward p60c-src, Lyn, and Lck PTK showed in general high Lyn/Src and moderate Lck/Src selectivity ratios. We found that the chi1 space constraints of the specialized amino acids, introduced at position 3 of the peptide lead 23, were not as important as the configuration of the Calpha of that residue to recognize the subtle chemical environment surrounding the active site of Src and Lck PTK, as reflected on the obtained Lck/Src selectivity ratios.
基于通过组合方法获得的p60c-src蛋白酪氨酸激酶（PTK）的有效底物YIYGSFK-NH2（1）（Km = 55 microM），我们设计并合成了一系列该酶的基于底物的构象和拓扑受限肽抑制剂，其IC50值在低微摩尔范围内（1-3 microM）。通过在肽抑制剂23（IC50 = 1.6 microM）的假定相互作用位点引入β-Me(2')Nal的四种立体异构体进行了“旋转异构体扫描”。这种取代产生了p60c-src PTK的选择性和强效抑制剂；然而，在它们之间未观察到效力上的实质性差异。这以及在形成二硫键的3的第2和7位残基（肽19-21）进行的“立体化学扫描”结果可能表明，酶活性位点没有严格的拓扑要求，因此只要抑制剂中的药效团模式得以保留，就能够实现重要的构象变化以结合配体。两种新的含碘强效非磷酸化酪氨酸类似物也被纳入我们的先导抑制序列23，产生了我们研究中迄今为止鉴定出的最有效的p60c-src PTK抑制剂。化合物29和30的IC50值分别为0.13和0.54 microM。肽29比母体肽1强420倍。对肽23-30对p60c-src、Lyn和Lck PTK的选择性研究总体上显示出高Lyn/Src和中等Lck/Src选择性比率。我们发现，在肽先导23的第3位引入的特殊氨基酸的chi1空间限制，不如该残基的Cα构型对识别Src和Lck PTK活性位点周围微妙化学环境重要，这反映在获得的Lck/Src选择性比率上。
