Farnesyl synthesis by these FPPS homologues is known to proceed through two subse quent steps. The reaction starts with the condensation of one molecule of DMAPP selleck chemicals Enzalutamide and one molecule of IPP, yielding the first product GPP. A second IPP molecule is condensed with GPP to form FPP as the final product. Accordingly, P. falciparum bifunctional FPPS GGPPS catalysis is a three step, four substrate process. Data derived from activity assays of rPfFPPS were ap parently hyperbolic to all tested substrate pairs, suggesting that rPfFPPS follows MM kinetics. As rPfFPPS catalyzes parallel and consecutive reactions, the interpretation of the apparent kinetic constants for this complex enzyme system is not trivial. The results presented here demonstrate that rPfFPPS is capable of synthesizing GPP, FPP, and GGPP from DMAPP and IPP, FPP and GGPP from GPP and IPP, and GGPP from FPP and IPP.

Assuming that rPfFPPS follows an ordered mechanism for substrate binding, when activity assays where carried out in the presence of DMAPP and IPP, there will be formation of GPP, followed by conversion Inhibitors,Modulators,Libraries of GPP to form FPP, which will Inhibitors,Modulators,Libraries be competitive inhibitors of the re actions catalyzed in steps 1, 2, and 3, since DMAPP, GPP, and FPP all compete for binding to the free enzyme active site. On the other hand, rPfFPPS activity measurements using GPP and IPP as substrates, there will be formation of FPP, which will be competitive inhibitors of the reactions catalyzed in steps 2 and 3, since GPP and FPP compete for binding to free enzyme. In this scenario, DMAPP, GPP, and FPP will also behave as non competitive inhibitors towards the second substrate, IPP.

This same issue has been described for human FPPS, where the authors clearly point out the difficulties of mechanistic studies modelling and interpretation. Evaluation of the apparent kinetic constants given in Table 1 should thus be interpreted with caution. Except for the substrate pair FPP IPP, the parameters presented for Inhibitors,Modulators,Libraries every other pair of substrates correspond to overall dissociation constants and overall Vmax values comprising the consecutive and par allel reactions that would be better described by modifi cations of the MM equation. Similar KM values for substrate pair IPP FPP were reported for Homo sapiens GGPPS and P. vivax GGPPS. The P. falciparum substrate pair IPP FPP also presented similar KM values, of 2. 4 0. 3 uM and 2.

06 0. 4 uM. The human FPPS enzyme has also been characterized, and KM values for IPP GPP of 0. 6 0. 1 uM and 0. 7 Inhibitors,Modulators,Libraries 0. 1 uM were reported. Again P. falciparum data for substrate pair IPP GPP in dicate similar KM for IPP and almost ten times larger KM value for GPP. These values, however, correspond to global apparent constants for steps 2 and Inhibitors,Modulators,Libraries 3. Considering varied substrates DMAPP, GPP, and FPP, selleck chemicals Alisertib there appears to be a trend in MM constant values, KM KM KM.