Structural Models For Molybdoenzymes

描述（由申请人提供）：钼和钨是仅有的具有已知生物功能的第二和第三行过渡元素。目前，已知的钼酶有50多种，其中有几种对人体健康具有临床意义（黄嘌呤和视黄醇氧化还原酶、亚硫酸盐氧化酶）。由于先天性缺乏“钼辅因子”，这些酶的活性同时存在致命的缺陷，这在儿童中已有很好的记录。亚硫酸盐氧化酶（SO）蛋白的点缺陷也可产生亚硫酸盐氧化酶缺乏症的神经症状。这些症状包括晶状体脱位、智力迟钝，严重时还会导致大脑发育迟缓和早死。本研究通过生物物理、生物化学和模型化合物的综合研究，探讨了亚硫酸盐氧化酶和其他氧化酶的基本性质。利用可变频率脉冲电子顺磁共振（EPR）技术，特别是电子自旋回波包络调制（ESEEM）、脉冲电子-核双共振（ENDOR）和电子-电子双共振（ELDOR）技术，通过氘、~（17）O和~（33）S标记，详细探测SO野生型和致病突变体中钼活性位点的周围环境，并通过补充理论计算。与人SO高度同源的重组小鼠SO将用于产生哺乳动物SO的生理和非生理突变体库，用于系统的结构、化学、机制和光谱研究。通过闪光光解和理论模拟研究了SO中钼和铁中心之间的分子内电子转移速率。

DESCRIPTION (provided by applicant): Molybdenum and tungsten are the only second and third row transition elements that have known biological functions. At present, over 50 molybdenum enzymes are known, and several are of clinical significance (xanthine and retinaldehyde oxidoreductases, sulfite oxidase) for human health. Fatal simultaneous deficiencies in the activities of these enzymes due to an inborn deficiency of a "molybdenum cofactor" have been well documented in children. Point defects in the sulfite oxidase (SO) protein can also produce the neurological symptoms of sulfite oxidase deficiency. These symptoms include dislocated ocular lenses, mental retardation, and, in severe cases, attenuated growth of the brain and early death. The research proposed here addresses the fundamental properties of sulfite oxidase and other molybdoenzymes by an integrated program of biophysical, biochemical and model compound studies. Variable frequency pulsed electron paramagnetic resonance (EPR) techniques, especially electron spin echo envelope modulation (ESEEM), pulsed electron-nuclear double resonance (ENDOR), and electron-electron double resonance (ELDOR) spectroscopies, will be used to probe in detail the surroundings of the molybdenum active site in wild-type and pathogenic mutants of SO through labeling with deuterium, 17O and 33S, and by complementary theoretical calculations. Recombinant mouse SO, which is highly homologous to human SO, will be used to generate a library of physiological and non- physiological mutants of mammalian SO for systematic structural, chemical, mechanistic and spectroscopic studies. The rates of intramolecular electron transfer between the molybdenum and iron centers of SO will be investigated by flash photolysis and theoretical modeling.