PMID:11825609
| Citation |
Pan, JJ, Kuo, TH, Chen, YK, Yang, LW and Liang, PH (2002) Insight into the activation mechanism of Escherichia coli octaprenyl pyrophosphate synthase derived from pre-steady-state kinetic analysis. Biochim. Biophys. Acta 1594:64-73 |
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| Abstract |
Octaprenyl pyrophosphate synthase (OPPs) catalyzes the sequential condensation of five molecules of isopentenyl pyrophosphate with farnesyl pyrophosphate to generate all-trans C40-octaprenyl pyrophosphate, which constitutes the side chain of ubiquinone. Due to the slow product release, a long-chain polyprenyl pyrophosphate synthase often requires detergent or another factor for optimal activity. Our previous studies in examining the activity enhancement of Escherichia coli undecaprenyl pyrophosphate synthase have demonstrated a switch of the rate-determining step from product release to isopentenyl pyrophosphate (IPP) condensation reaction in the presence of Triton [12]. In order to understand the mechanism of enzyme activation for E. coli OPPs, a single-turnover reaction was performed and the measured IPP condensation rate (2 s(-1)) was 100 times larger than the steady-state rate (0.02 s(-1)). The high molecular weight fractions and Triton could accelerate the steady-state rate by 3-fold (0.06 s(-1)) but insufficient to cause full activation (100-fold). A burst product formation was observed in enzyme multiple turnovers indicating a slow product release. |
| Links | |
| Keywords |
Alkyl and Aryl Transferases/metabolism; Enzyme Activation; Escherichia coli/enzymology; Hemiterpenes; Hydrogen-Ion Concentration; Kinetics; Organophosphorus Compounds/metabolism; Polyethylene Glycols; Polyisoprenyl Phosphates/biosynthesis; Polyisoprenyl Phosphates/metabolism; Sesquiterpenes; Temperature |
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