Preparation and reactivity studies of synthetic microperoxidases containing b-type heme.
In order to create a heme environment that permits biomimicry of heme-containing peroxidases, a number of new hemin-peptide complexes--hemin-2(18)-glycyl-L-histidine methyl ester (HGH), hemin-2(18)-glycyl-glycyl-L-histidine methyl ester (HGGH), and hemin-2,18-bis(glycyl-glycyl-L-histidine methyl ester) (H2GGH)--have been prepared by condensation of glycyl-L-histidine methyl ester or glycyl-glycyl-L-histidine methyl ester with the propionic side chains of hemin. Characterization by means of UV/vis- and 1H NMR spectroscopy as well as cyclic- and differential pulse voltammetry indicates the formation of five-coordinate complexes in the case of HGH and HGGH, with histidine as an axial ligand. In the case of H2GGH, a six-coordinate complex with both imidazoles coordinated to the iron center appears to be formed. However, 1H NMR of H2GGH reveals the existence of an equilibrium between low-spin six-coordinate and high-spin five-coordinate species in solution. The catalytic activity of the hemin-peptide complexes towards several organic substrates, such as p-cresol, L-tyrosine methyl ester, and ABTS, has been investigated. It was found that not only the five-coordinate HGH and HGGH complexes, but also the six-coordinate H2GGH, catalyze the oxidation of substrates by H2O2. The longer and less strained peptide arm provides the HGGH complex with a slightly higher catalytic efficiency, as compared with HGH, due to formation of more stable intermediate complexes.
Ryabova
Ekaterina S
ES
Inorganic Chemistry, Chemical Center, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
Dikiy
Alexander
A
Hesslein
Ashley E
AE
Bjerrum
Morten J
MJ
Ciurli
Stefano
S
Nordlander
Ebbe
E
D002384:Catalysis; D006418:Heme / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D007700:Kinetics; D008024:Ligands; D018716:Molecular Mimicry; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000138:chemical synthesis* / Q000737:chemistry; D013329:Structure-Activity Relationship
D008024:Ligands; D009842:Oligopeptides; D006418:Heme; D006861:Hydrogen Peroxide; D010544:Peroxidases; C021799:microperoxidase