Sumathi S, Dasgupta D, Vaidyanathan C S
Department of Biochemistry, Indian Institute of Science, Bangalore, India.
Indian J Biochem Biophys. 1998 Oct;35(5):266-72.
The inactivation of 3-HBA-6-hydroxylase isolated from Micrococcus species by phenylglyoxal and protection offered by 3-HBA against inactivation indicate the presence of arginine residue at or near the substrate binding site. The loss of enzyme activity was time and concentration dependent and displayed pseudo-first order kinetics. A 'n' value of 0.9 was obtained thus suggesting the modification of a single arginine residue per active site which led to the loss of enzyme activity. The enzyme activity could be restored by extensive dialysis at neutral pH. Quenching of the intrinsic fluorescence and reduction in the ellipticity value at 280 nm in the near-UV CD spectrum of the enzyme was noticed after its treatment with phenylglyoxal. These observations probably imply distinct perturbations in the environment of adjacent aromatic amino acid residues such as tryptophan as a consequence of arginine modification.
从微球菌属分离出的3 - HBA - 6 - 羟化酶被苯乙二醛灭活以及3 - HBA对其灭活的保护作用表明在底物结合位点或其附近存在精氨酸残基。酶活性的丧失具有时间和浓度依赖性，并呈现假一级动力学。由此获得的“n”值为0.9，表明每个活性位点有一个精氨酸残基被修饰，导致酶活性丧失。通过在中性pH下进行广泛透析可恢复酶活性。用苯乙二醛处理该酶后，观察到其固有荧光猝灭以及近紫外圆二色光谱中280 nm处椭圆率值降低。这些观察结果可能意味着由于精氨酸修饰，相邻芳香族氨基酸残基（如色氨酸）的环境发生了明显扰动。
