Alhamadsheh Mamoun M, Musayev Faik, Komissarov Andrey A, Sachdeva Sarbjot, Wright H Tonie, Scarsdale Neel, Florova Galina, Reynolds Kevin A
Department of Chemistry, Portland State University, Portland, OR 97207, USA.
Chem Biol. 2007 May;14(5):513-24. doi: 10.1016/j.chembiol.2007.03.013.
The first step of the reaction catalyzed by the homodimeric FabH from a dissociated fatty acid synthase is acyl transfer from acyl-CoA to an active site cysteine. We report that C1 to C10 alkyl-CoA disulfides irreversibly inhibit Escherichia coli FabH (ecFabH) and Mycobacterium tuberculosis FabH with relative efficiencies that reflect these enzymes' differential acyl-group specificity. Crystallographic and kinetic studies with MeSSCoA show rapid inhibition of one monomer of ecFabH through formation of a methyl disulfide conjugate with this cysteine. Reaction of the second subunit with either MeSSCoA or acetyl-CoA is much slower. In the presence of malonyl-ACP, the acylation rate of the second subunit is restored to that of the native ecFabH. These observations suggest a catalytic model in which a structurally disordered apo-ecFabH dimer orders on binding either the first substrate, acetyl-CoA, or the inhibitor MeSSCoA, and is restored to a disordered state on binding of malonyl-ACP.
由解离的脂肪酸合酶的同二聚体FabH催化的反应的第一步是酰基从酰基辅酶A转移至活性位点半胱氨酸。我们报道，C1至C10烷基 - 辅酶A二硫化物以反映这些酶不同酰基特异性的相对效率不可逆地抑制大肠杆菌FabH（ecFabH）和结核分枝杆菌FabH。用MeSSCoA进行的晶体学和动力学研究表明，通过与该半胱氨酸形成甲基二硫化物共轭物，ecFabH的一个单体被快速抑制。第二个亚基与MeSSCoA或乙酰辅酶A的反应要慢得多。在丙二酸单酰 - ACP存在下，第二个亚基的酰化速率恢复到天然ecFabH的酰化速率。这些观察结果提示了一种催化模型，其中结构无序的脱辅基ecFabH二聚体在结合第一个底物乙酰辅酶A或抑制剂MeSSCoA时有序化，并在结合丙二酸单酰 - ACP时恢复到无序状态。
