产品内容
本酶催化的反应为GDP-4-Dehydro-alpha-D-Rhamnose + L-Glutamate = GDP-4-Dehydro-3,6-Dideoxy-alpha-D-Mannose + 2-Oxoglutarate + NH3 (Overall Reaction);;(1a) GDP-4-Dehydro-alpha-D-Rhamnose + L-Glutamate = 2-GDP-[(2S,3S,6R)-5-Amino-6-Methyl-3,6-Dihydro-2H-Pyran-3-Ol] + 2-Oxoglutarate + H2O;;(1b) 2-GDP-[(2S,3S,6R)-5-Amino-6-Methyl-3,6-Dihydro-2H-Pyran-3-Ol] = 2-GDP-[(2S,3S,6R)-5-Imino-6-Methyloxan-3-Ol] (Spontaneous);;(1c) GDP-2-[(2S,3S,6R)-5-Imino-6-Methyloxan-3-Ol] + H2O = GDP-4-Dehydro-3,6-Dideoxy-alpha-D-Mannose + NH3 (Spontaneous),系统名称为GDP-4-Dehydro-alpha-D-Rhamnose 3-Hydro-Lyase,该酶参与β-L-colitose的生物合成,是一种独特的依赖维生素B6的酶。在催化第一步中,结合的磷酸吡哆醛(PLP)辅因子以L-谷氨酸为氨基供体被转氨为维生素B6的磷酸吡哆胺(PMP)形式。PMP辅因子随后与糖底物形成席夫碱,所得加合物经1,4-脱水消除3-OH基团。产物从酶上水解释放,恢复PLP辅因子,并释放一个不稳定的烯胺中间体。该中间体互变异构形成亚胺形式,后者自发水解,释放氨并形成终产物。