Essential amino acids involved in the catalysis of cis-type undecaprenyl pyrophosphate synthase and trans-type octaprenyl pyrophosphate synthase from E. coli and their reaction mechanisms
Date Issued
2004
Date
2004
Author(s)
Li, Shih-Chun
DOI
zh-TW
Abstract
Isoprenoids are widely distributed natural polymers containing isopentenyl pyrophosphate (IPP) as building block. The biosyntheses of isoprenoids are carried out by a group of enzymes called prenyltransferases which catalyze the head to tail condensation between IPP and farnesyl pyrophosphate (FPP) to make linear long-chain products. These FPP-utilizing enzymes play essential biological role, e.g. the C55 undecaprenyl pyrophosphate (UPP) generated by UPP synthase (UPPs) serves as a lipid carrier to transport lipid II across the bacterial cell membrane for peptidoglycan synthesis of the cell wall; Octaprenyl pyrophosphate synthase (OPPs) catalyzes the sequential condensation of five molecules of isopentenyl pyrophosphate with farnesyl pyrophosphate (FPP) to generate all-trans C40-octaprenyl pyrophosphate, which constitutes the side chain of ubiquinone. Previously, we have solved the complete kinetic pathways and 3-D structures of E. coli UPPs and OPPs. Based on the crystal structure, some amino acids in neighborhood of the active site are proposed to play important roles in substrate binding and the reaction. However, the amino acids which act as general acid and base in the catalysis have not been identified. In this study, we utilized pH profile in conjunction with site-directed mutagenesis to examine the important residues. Some novel method of study has also been developed.
Subjects
類異戊二烯
轉移酵素
合成
焦磷酸
UPPs
prenyltransferases
farnesyl pyrophosphate
OPPs
isopentenyl pyrophosphate
Isoprenoids
Type
other
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