Combining medium effects and cofactor catalysis: metal-coordinated synzymes accelerate phosphate transfer by 10(8).
The systematic exploration of the modification of polyethylene imine with guanidinium and octyl groups has led to the identification of a catalyst, CD6, which accelerates the phosphate transfer reaction of HPNP (2-hydroxypropyl-4-nitrophenyl phosphate) in the presence of divalent metals such as Zn(2+), Co(2+), Mg(2+) or Ni(2+). CD6 exhibits saturation kinetics that are described by Michaelis-Menten parameters K(m) ranging from 2.5-8 mM and k(cat) ranging from 0.0014-0.09 s(-1). For Zn(II)-CD6 this corresponds to an overall acceleration k(cat)/k(uncat) of 3.8x10(5) and a catalytic proficiency (k(cat)/K(m))/k(uncat) of 1.5x10(8). Catalysis by Zn(II)-CD6 is specifically inhibited by inorganic phosphate, allowing turnover regulation by product inhibition. This effect stands in contrast to Zn(II)-catalysed transesterification of HPNP in water or by the synzymes Co(II)-CD6 and Ni(II)-CD6, with which no such interference by product is observed. These characteristics render synzyme Zn(II)-CD6 an efficient enzyme model that reflects enzyme-like properties in a wide range of features.
Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK.
Frédéric
F
Avenier
Florian
F
Hollfelder
D002384:Catalysis; D002413:Cations, Divalent; D018360:Crystallography, X-Ray; D004798:Enzymes / Q000737:chemistry* / Q000378:metabolism; D008670:Metals / Q000737:chemistry*; D008958:Models, Molecular; D010755:Organophosphates; D009943:Organophosphorus Compounds; D010261:Paraoxon / Q000031:analogs & derivatives* / Q000737:chemistry; D010710:Phosphates / Q000737:chemistry*; D011095:Polyethylenes / Q000737:chemistry*
C436487:2-(hydroxypropyl)-4-nitrophenyl phosphate; D002413:Cations, Divalent; D004798:Enzymes; D008670:Metals; D010755:Organophosphates; D009943:Organophosphorus Compounds; D010710:Phosphates; D011095:Polyethylenes; D010261:Paraoxon