Hlavica Peter
Walther-Straub Institut für Pharmakologie und Toxikologie der LMU, Goethestrasse 33, D-80336 München, Germany.
Biochim Biophys Acta. 2013 Jan;1834(1):205-20. doi: 10.1016/j.bbapap.2012.09.012. Epub 2012 Sep 23.
Fungi belong to the large kingdom of lower eukaryotic organisms encompassing yeasts along with filamentous and dimorphic members. Microbial P450 enzymes have contributed to exploration of and adaptation to diverse ecological niches such as conversion of lipophilic compounds to more hydrophilic derivatives or degradation of a vast array of environmental toxicants. To better understand diversification of the catalytic behavior of fungal P450s, detailed insight into the molecular machinery steering oxidative attack on the distinctly structured endogenous and xenobiotic substrates is of preeminent interest. Based on a general, CYP102A1-related template the bulk of predicted substrate/inhibitor-binding determinants were shown to cluster near the distal heme face within the six known substrate recognition sites (SRSs) made up by the α-helical B'/F/G/I tetrad, the B'-C interhelical loop and strands of the β6-sheet, population density being highest in the structurally flexible SRS-1 and SRS-4 domains, showing a low degree of conservation. Reactivity toward ligands favorably coincides with the lipophilicity/hydrophilicity profile and bulkiness of critical amino acids acting as selective filters. Some decisive elements may also serve in maintenance of catalytic competence via their action as gatekeepers directing substrate access/positioning or stabilizers of the heme environment enabling dioxygen activation. Non-SRS residues seem to control spin state equilibria and attract redox partners by electrostatic forces. Of note, the inhibitory potency of azole-type fungicides is likely to arise from perturbation of the complex interplay of the mechanistic principles addressed above. Knowledge-supported exploitation of the topological data will be helpful in the manufacture of commodity/specialty chemicals as well as therapeutic agents. Also, engineered fungal P450s may be used to improve pollutant-specific bioremediation of contaminated soils.
真菌属于低等真核生物的大类，包括酵母以及丝状和双态成员。微生物P450酶有助于探索和适应各种生态位，例如将亲脂性化合物转化为更具亲水性的衍生物或降解大量环境毒物。为了更好地理解真菌P450催化行为的多样性，深入了解引导对结构独特的内源性和外源性底物进行氧化攻击的分子机制具有至关重要的意义。基于一个通用的、与CYP102A1相关的模板，大部分预测的底物/抑制剂结合决定因素显示聚集在由α-螺旋B'/F/G/I四联体、B'-C螺旋间环和β6-折叠链组成的六个已知底物识别位点（SRS）内的远侧血红素表面附近，在结构灵活的SRS-1和SRS-4结构域中种群密度最高，显示出低程度的保守性。对配体的反应性与作为选择性过滤器的关键氨基酸的亲脂性/亲水性特征和体积有利地一致。一些决定性元素还可能通过作为引导底物进入/定位的守门人或使血红素环境稳定从而实现双氧激活的作用来维持催化能力。非SRS残基似乎控制自旋态平衡并通过静电力吸引氧化还原伙伴。值得注意的是，唑类杀菌剂的抑制效力可能源于上述机制原理复杂相互作用的扰动。基于知识利用拓扑数据将有助于制造商品/特种化学品以及治疗剂。此外，工程化的真菌P450可用于改善污染土壤中特定污染物的生物修复。
