A peptide dendrimer enzyme model with a single catalytic site at the core.
Catalytic esterase peptide dendrimers with a core active site were discovered by functional screening of a 65,536-member combinatorial library of third-generation peptide dendrimers using fluorogenic 1-acyloxypyrene-3,6,8-trisulfonates as substrates. In the best catalyst, RMG3, ((AcTyrThr)(8)(DapTrpGly)(4)(DapArgSerGly)(2)DapHisSerNH2), ester hydrolysis is catalyzed by a single catalytic histidine residue at the dendrimer core. A pair of arginine residues in the first-generation branch assists substrate binding. The catalytic proficiency of dendrimer RMG3 (kcat/KM = 860 M(-1) min(-1) at pH 6.9) per catalytic site is comparable to that of the multivalent esterase dendrimer A3 ((AcHisSer)(8)(DapHisSer)(4)(DapHisSer)2DapHisSerNH2) which has fifteen histidines and five catalytic sites (Delort, E. et al. J. Am. Chem. Soc. 2004, 126, 15642-15643). Remarkably, catalysis in the single site dendrimer RMG3 is enhanced by the outer dendritic branches consisting of aromatic amino acids. These interactions take place in a relatively compact conformation similar to a molten globule protein as demonstrated by diffusion NMR. In another dendrimer, HG3 ((AcIlePro)(8)(DapIleThr)(4)(DapHisAla)(2)DapHisLeuNH2) by contrast, catalysis by a core of three histidine residues is unaffected by the outer dendritic layers. Dendrimer HG3 or its core HG1 exhibit comparable activity to the first-generation dendrimer A1 ((AcHisSer)(2)DapHisSerNH2). The compactness of dendrimer HG3 in solution is close to that a denatured peptide. These experiments document the first esterase peptide dendrimer enzyme models with a single catalytic site and suggest a possible relationship between packing and catalysis in these systems.
Javor
Sacha
S
Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, 3012 Berne, Switzerland.
Delort
Estelle
E
Darbre
Tamis
T
Reymond
Jean-Louis
JL
D000595:Amino Acid Sequence; D020134:Catalytic Domain; D030562:Databases, Protein; D050091:Dendrimers / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D004058:Diffusion; D004950:Esterases / Q000737:chemistry* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008954:Models, Biological; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*
D050091:Dendrimers; D010455:Peptides; D004950:Esterases