McArdell J E, Atkinson T, Bruton C J
Eur J Biochem. 1982 Jul;125(2):361-6. doi: 10.1111/j.1432-1033.1982.tb06692.x.
Brown MX-5BR specifically and irreversibly inactivates tryptophanyl-tRNA synthetase from Bacillus stearothermophilus at pH 8.5. The enzyme is protected from inactivation by the substrates tryptophan and ATP and to lesser extents by ADP, AMP, the product inorganic pyrophosphate and other nucleotides such as GTP. The Kd of the pure reactive dye for the enzyme was measured to be 6.7 X 10(-6) M. The Km values of the two substrates tryptophan and MgATP were found to be 1 x 10(-5) M and 5 x 10(-5) M respectively. The aminated dye is a competitive inhibitor of tryptophanyl-tRNA synthetase with respect to both tryptophan and MgATP with Ki values of 2 x 10(-4) M against both substrates. The use of this dye as an active-site-directed affinity label is discussed.
Brown MX - 5BR在pH 8.5时能特异性且不可逆地使嗜热脂肪芽孢杆菌的色氨酰 - tRNA合成酶失活。该酶可被底物色氨酸和ATP保护而不被失活，在较小程度上也可被ADP、AMP、产物无机焦磷酸以及其他核苷酸如GTP保护。测得该纯活性染料对该酶的解离常数（Kd）为6.7×10⁻⁶ M。发现色氨酸和MgATP这两种底物的米氏常数（Km）分别为1×10⁻⁵ M和5×10⁻⁵ M。胺化染料是色氨酰 - tRNA合成酶针对色氨酸和MgATP的竞争性抑制剂，对两种底物的抑制常数（Ki）均为2×10⁻⁴ M。文中讨论了将这种染料用作活性位点导向亲和标记物的用途。
