COVALENT FLAVIN COENZYMES IN FLAVOENZYME CATALYSIS

对8 α-S-半胱氨酰的结构和作用机理进行了研究 含FAD的酶：单胺氧化酶B（MAO B）和单胺氧化酶 A（MAO A）。将在酵母中表达的人MAO B和MAO A纯化， 表征，并与物理和化学性质进行比较， 人胎盘单胺氧化酶A和牛肝单胺氧化酶B。了系统的调查 环取代基的影响的结合和CH键断裂的速度， 苄胺底物将从目前对牛单胺氧化酶B的研究中扩展 重组人单胺氧化酶A和单胺氧化酶B。环取代基效应 苯乙胺底物类似物对CH键结合和速率的影响 还将用MAO A和MAO B研究裂解，结果 与苄胺数据进行比较，以提供有关 空间效应对催化作用的影响。 有助于在MAO B和MAO A中进行氢转移步骤 与J. Klinman博士合作，U.加利福尼亚州，伯克利证据 氨基酸自由基的催化参与和身份， 将在MAO A和MAO B中寻找氢原子提取的功能 使用天然和同位素标记的酶的ESR和ENDOR。的 氧化/还原电位的OX/SQ和SQ/HQ对的 在MAO B和MAO A中的共价黄素辅酶将使用 分光库仑法这些研究的结果将提供新的 深入了解了MAO A和MAO B的催化机理，并提供了 为开发每种酶的特异性抑制剂奠定了基础， 作为药物治疗的靶点具有神经药理学的重要性。 抗 临床上使用的抑制剂是MAO A抑制剂， 单胺氧化酶B抑制剂是加强左旋多巴治疗的患者， 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.