PHYSICAL-CHEMICAL ANALYSIS OF PEROXIDASES

木质素酶是一种木质素降解酶，催化木质素的氧化降解， 木质素的丙基骨架的裂解，也催化H2 O2 广泛的底物的依赖性氧化，包括通常 最困难和速率限制的初始氧化步骤 许多环境持久性异生物质的降解。不 只能引发许多底物的降解，但催化所有 这些步骤的二氧化碳。这些酶在管理中提供了巨大的潜力 环境废物。虽然这些木质素降解酶具有许多 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质素酶活性，这些酶 其独特之处在于其氧化极高还原性底物的能力 潜力该活性具有低的pH最适值，并且由 pK在羧基电离范围内的电离。初始 H2 O2活化步骤不受单个可电离基团控制 在微酸性区域具有pK，不同于所有其他过氧化物酶， 这表明了一种不同的机制，可以解释这种差异。 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 的木质素酶，并比较和对比这些与其他 过氧化物酶提供基本的设计原则，为合成类似物 和基因工程来实现这种无处不在的功能。局部结构 在H2 O2中形成的中间态的活性位点 木质素酶和其他过氧化物酶的依赖性初级反应将是 使用X射线吸收光谱法进行研究， 配体环境将用傅立叶变换红外探测 谱同工酶和结构功能的比较 通过定点诱变产生的变化提供了一种独特的方法， 确定反应性和底物特异性的结构基础 并建立一个基于结构的机制， 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.