PHYSICAL-CHEMICAL ANALYSIS OF PEROXIDASES

木质素酶，催化氧化的木质素降解酶 木质素丙基主链的裂解，也催化过氧化氢 大量底物的依赖氧化，包括经常 最困难和限速的初始氧化步骤 降解许多对环境具有持久性的外来物。它不是 只能引发许多底物的降解，但能催化所有 这些步骤会转化为二氧化碳。这些酶在管理上提供了巨大的潜力。 环境垃圾。尽管这些木质素降解酶有许多 与其他过氧化物酶相似的特性和性质，其他 过氧化物酶不显示木素酶活性，这些酶是 其独特之处在于能够氧化极高还原程度的底物 潜力。该活性的最适pH值较低，并受 在羧基电离范围内用pk进行电离。首字母 过氧化氢的活化步骤不受单个可电离基团的控制 与所有其他过氧化物酶不同的是，在弱酸性区域有PK， 提出了一种不同的机制，这可能解释了 反应性。拟议的研究试图在分子水平上澄清， 活性中心附近的结构-功能关系 并将这些酶与其他 过氧化物酶为合成类似物提供基本设计原则 以及这种无处不在的功能的基因工程。地方性结构 在过氧化氢中形成的中间态的活性中心 木质素酶和其他过氧化物酶的依赖初级反应将是 使用x射线吸收光谱分析，而远端袋 用傅里叶变换红外探测配基环境 光谱学。同工酶与结构--功能的比较 定点突变产生的变化提供了一种独特的方法 确定反应性和底物专一性的结构基础 并建立一个基于结构的机制，为这些潜在的有用 废物降解酶。

Ligninase, the lignin degrading enzyme which catalyzes the oxidative cleavage of the propyl backbone of lignin, also catalyzes the H2O2 dependent oxidation of a wide range of substrates, including the often most difficult and rate limiting initial oxidative step in the degradation of many environmentally persistent xenobiotics. It is not only able to initiate degradation of many substrates but to catalyze all these steps to CO2. These enzymes offer great potential in the management of environmental waste. Although these lignin degrading enzymes have many characteristics and properties similar to other peroxidases, other peroxidases do not exhibit ligninase activity and these enzymes are unique in their ability to oxidize substrates of extremely high reduction potential. This activity has a low pH optimum and is controlled by an ionization with a pK in the range of carboxyl ionization. The initial step of H2O2 activation is not controlled by a single ionizable group having a pK in the slightly acidic region, unlike all other peroxidase, suggesting a different mechanism which may account for the difference in reactivity. The proposed studies attempt to clarify on a molecular level, the structure -- function relationship in the vicinity of the active site of the ligninase enzymes and to compare and contrast these with other peroxidases to provide the basic design principles for synthetic analogs and genetic engineering of this ubiquitous function. The local structure of the active site in the intermediate states formed in the H2O2 dependent primary reactions of ligninase and other peroxidases will be investigated using x-ray absorption spectroscopy while the distal pocket ligand environment will be probed with Fourier transformed infrared spectroscopy. Comparison of the isoenzymes and structure- - function changes produced by site directed mutagenesis offer a unique approach to identify the structural basis for reactivity and substrate specificity and establish a structure based mechanism for these potentially useful waste degrading enzymes.