Catalytic and inhibiting effect of amino acids on the porphyrin metallation reactions

In the present work, using the interaction of tetra-(4-sulfophenyl)porphyrin with copper(II) chloride as an example, it has been shown how different amino acid additives (glycine, valine, leucine and tryptophan) catalyze or inhibit the formation of Cu-porphyrin as a function of the chemical environment (borate buffer (pH7.4), DMSO) and the concentration of the additive. It has been demonstrated that the type of amino acid affects the complexation reaction rate. Possible mechanisms of metalloporphyrin formation and the ways of their acceleration are discussed.

Structure-function investigation of a deoxyribozyme with dual chelatase and peroxidase activities

PS2.M, an 18-nucleotide DNA molecule, has been shown to be a dual enzyme for porphyrin metallation and, when complexed with hemin, for peroxidation. To date, detailed information has not been available on either the actively folded structure of PS2.M or on the contribution of specific nucleotides within it toward the peroxidase activity. Here, we report a variety of experiments that probe the structure and function of PS2.M as well as of a number of point mutants of PS2.M. Based on these experiments, a structural model for the folding of PS2.M and the location of a functionally relevant hemin-binding site are proposed. A key finding is that PS2.M, originally obtained by in vitro selection from a random-sequence DNA library, is uniquely suited for its catalysis of peroxidation; all point mutants examined showed significantly poorer catalytic activity than PS2.M itself.

The synthesis of specifically metallated heterobimetallic dimeric porphyrins

A series of conjugated mixed metal heteroporphyrin dimers has been prepared using Wittig chemistry. They can be synthesized from a double Wittig reaction between porphyrin phosphonium salts and phthalaldehydes, or from stepwise Wittig reactions. This allows both symmetrical and unsymmetrical dimers to be prepared with complete control of porphyrin metallation.