Sugiyama N, Sasaki T, Iwamoto M, Abiko Y
Research Institute, Daiichi Seiyaku Co., Tokyo, Japan.
Biochim Biophys Acta. 1988 Jan 4;952(1):1-7. doi: 10.1016/0167-4838(88)90094-5.
Peptide T-11, a carboxyl terminal tryptic fragment of alpha 2-plasmin inhibitor, inhibits the reversible first step of the reaction between plasmin and alpha 2-plasmin inhibitor. To elucidate which amino-acid residues played a important role in the inhibitory activity of peptide T-11, we prepared the various synthetic derivatives of peptide T-11 and determined the peptide concentration that inhibited the apparent rate constant of the reaction between plasmin and alpha 2-plasmin inhibitor by 50% (IC50). Peptide III, which lacked the residues Gly-1 to Pro-7 of peptide I (peptide T-11), had a strong inhibitory activity, like peptide I (IC50: peptide I, 7 microM; peptide III, 13 microM). The peptides that lacked the Leu-9 and Lys-10 or Lys-26 of peptide III showed much weaker activity, and the loss or amidation of the C-terminal lysine of peptide III also markedly reduced the inhibitory activity. Peptide III competitively inhibited the binding of [14C]tranexamic acid to kringle 1 + 2 + 3 (K1-3) and kringle 4 (K4) in a binding assay performed by the gel-diffusion method. The respective dissociation constants (Kd) of peptide III for K1-3 and K4 were 0.85 microM and 35.2 microM. These data suggest that the amino residue of Lys-10 and the carboxylic acid of Lys-26 in peptide T-11 play crucial roles in the ionic binding of alpha 2-plasmin inhibitor to the tranexamic acid-binding site (lysine-binding site) of plasminogen. Peptide T-11: H-G-D-K-L-F-G-P-D-L-K-L-V-P-P-M-E-E-D-Y-P-Q-F-G-S-P-K-OH.
肽T-11是α2-纤溶酶抑制剂的羧基末端胰蛋白酶片段，可抑制纤溶酶与α2-纤溶酶抑制剂反应的可逆第一步。为了阐明哪些氨基酸残基在肽T-11的抑制活性中起重要作用，我们制备了肽T-11的各种合成衍生物，并确定了使纤溶酶与α2-纤溶酶抑制剂反应的表观速率常数抑制50%（IC50）时的肽浓度。肽III缺少肽I（肽T-11）的Gly-1至Pro-7残基，具有很强的抑制活性，与肽I类似（IC50：肽I，7μM；肽III，13μM）。缺少肽III的Leu-9和Lys-10或Lys-26的肽活性弱得多，肽III的C末端赖氨酸缺失或酰胺化也显著降低了抑制活性。在凝胶扩散法进行的结合试验中，肽III竞争性抑制[14C]氨甲环酸与kringle 1 + 2 + 3（K1-3）和kringle 4（K4）的结合。肽III与K1-3和K4的各自解离常数（Kd）分别为0.85μM和35.2μM。这些数据表明，肽T-11中Lys-10的氨基残基和Lys-26的羧基在α2-纤溶酶抑制剂与纤溶酶原的氨甲环酸结合位点（赖氨酸结合位点）的离子结合中起关键作用。肽T-11：H-G-D-K-L-F-G-P-D-L-K-L-V-P-P-M-E-E-D-Y-P-Q-F-G-S-P-K-OH。
