Hashizume H, Shimomura M
Department of Chemistry, University of Shizuoka, Japan.
Biochem Int. 1987 Jul;15(1):19-25.
Trp-155 in bovine DNase A (EC 3.1.4.5) appeared to be unessential for the enzymatic activity for the following reasons: (1) A unique peptide which suggests the environmental difference of Trp-155 was obtained from porcine pancreatic DNase A. (2) Inactivation of the porcine DNase A by NBS modification was fairly paralleled with a decrease in the CD signal, which is characteristic of the "buried" tryptophan in the hydrophobic region (trp-191 in bovine DNase) but not of tryptophans in the hydrophilic portion. Binding of DNase to the poly I: poly C double helix confirmed the important role of this tryptophan.
牛脱氧核糖核酸酶A（EC 3.1.4.5）中的色氨酸-155对酶活性似乎并非必不可少，原因如下：（1）从猪胰脱氧核糖核酸酶A中获得了一个独特的肽段，这表明色氨酸-155所处环境存在差异。（2）NBS修饰使猪脱氧核糖核酸酶A失活，这与圆二色（CD）信号的降低相当平行，CD信号是疏水区域中“埋藏”色氨酸（牛脱氧核糖核酸酶中的色氨酸-191）的特征，而不是亲水区色氨酸的特征。脱氧核糖核酸酶与聚肌苷酸：聚胞苷酸双螺旋的结合证实了该色氨酸的重要作用。
