立体化学
基质(水族馆)
酶
化学
水解酶
生物碱
葡萄糖苷酶
突变体
生物合成
阿玛林
生物化学
生物
基因
生态学
神经科学
作者
Liqun Xia,Martin Ruppert,Meitian Wang,Santosh Panjikar,Haili Lin,Chitra Rajendran,Leif Barleben,Joachim Stöckigt
摘要
Two similar enzymes with different biosynthetic function in one species have evolved to catalyze two distinct reactions. X-ray structures of both enzymes help reveal their most important differences. The Rauvolfia alkaloid biosynthetic network harbors two O-glucosidases: raucaffricine glucosidase (RG), which hydrolyses raucaffricine to an intermediate downstream in the ajmaline pathway, and strictosidine glucosidase (SG), which operates upstream. RG converts strictosidine, the substrate of SG, but SG does not accept raucaffricine. Now elucidation of crystal structures of RG, inactive RG-E186Q mutant, and its complexes with ligands dihydro-raucaffricine and secologanin reveals that it is the “wider gate” of RG that allows strictosidine to enter the catalytic site, whereas the “slot-like” entrance of SG prohibits access by raucaffricine. Trp392 in RG and Trp388 in SG control the gate shape and acceptance of substrates. Ser390 directs the conformation of Trp392. 3D structures, supported by site-directed mutations and kinetic data of RG and SG, provide a structural and catalytic explanation of substrate specificity and deeper insights into O-glucosidase chemistry.
科研通智能强力驱动
Strongly Powered by AbleSci AI