COVALENT FLAVIN COENZYMES IN FLAVOENZYME CATALYSIS

对8α-S-半胱氨酸基的机理和结构进行了研究 含FAD酶：单胺氧化酶B(MAO B)和单胺氧化酶 A(毛A)。在酵母中表达的人MAO B和MAO A将得到纯化和 对其进行了表征，并与其物理化学性质进行了比较 人胎盘MAO A和牛肝MAO B的系统研究 环取代基对CH键键合和裂解速率的影响 苄胺底物将在目前对牛MAO B的研究基础上得到扩展 环取代基对重组人MAO A和MAO B的影响 苯乙胺底物类似物对CH键结合率的影响 卵裂也将与MAO A和MAO B一起调查，结果是 与苄胺数据进行比较，以提供详细的信息 空间位阻对催化剂的影响。隧道效应是否 有助于MAO B和MAO A中的氢转移步骤将完成 与加州大学伯克利分校的J.Klinman博士合作。证据： 一种氨基酸自由基的催化参与和鉴定 在氢原子抽象中的功能将在MAO A和MAO B中寻找 使用天然和同位素标记的酶的ESR和Endor。这个 OX/SQ和SQ/HQ对的氧化/还原电势 MAO B和MAO A中的共价黄素辅酶将用 光谱库仑测定法。这些研究的结果应该会提供新的 对MAO A和MAO B的催化机理的见解和提供 开发针对每种酶的特定抑制剂的基础 作为药物治疗的靶点具有神经药理学上的重要性。反- 临床上使用的抑郁症是MAO A抑制剂，而临床上使用的 MAO B抑制剂是加强L-多巴治疗的慢性阻塞性肺疾病患者 帕金森氏症。

Mechanistic and structural studies are proposed on the 8alpha-S-cysteinyl FAD-containing enzymes: monoamine oxidase B (MAO B) and monoamine oxidase A (MAO A). Human MAO B and MAO A expressed in yeast will be purified and characterized, and compared with the physical and chemical properties of human placental MAO A and bovine liver MAO B. A systematic investigation of ring substituent effects on the binding and rate of CH bond cleavage of benzylamine substrates will be extended from current work on bovine MAO B to recombinant human MAO A and MAO B. Ring-substituent effects on phenethylamine substrate analogs on the binding and rate of CH bond cleavage will also be investigated with MAO A and MAO B and the results compared with the benzylamine data to provide detailed information on steric effects on catalysis.Investigations into whether tunneling contributes to the hydrogen transfer step in MAO B and MAO A will be done in collaboration with Dr. J. Klinman, U. Calif., Berkeley. Evidence for the catalytic involvement and identity of an amino acid radical which may function in hydrogen atom abstraction will be sought in MAO A and MAO B using ESR and ENDOR of native and isotopically labeled enzymes. The oxidation/reduction potentials for the OX/SQ and SQ/HQ couples of the covalent flavin coenzymes in MAO B and in MAO A will be determined using spectrocoulometry. The results of these studies should provide new insights into the catalytic mechanisms of MAO A and of MAO B and provide a basis for the development of specific inhibitors for each enzyme which are of neuropharmacological importance as targets for drug therapy. Anti- depressants used clinically are MAO A inhibitors while the clinical use of MAO B inhibitors is to potentiate L-Dopa therapy of patients with Parkinson's Disease.