Effect of cationic and anionic porphyrins on the structure and activity of adenosine deaminase

Abstract

Kinetic and structural studies have been carried out on the effects of meso-tetrakis(4-sulfonatophenyl)- porphyrin (H2TPPS4) as an anionic and meso-tetrakis(3-N-methyl-pyridyl)porphyrin (H2TMPYP) as a cationic porphyrin with adenosine deaminase (ADA) in 25 mM citrate/phosphate buffer, pH = 4-8, at 37 °C using UVvis spectrophotometry, circular dichroism (CD), fluorescence spectrophotometry as well as molecular dynamics (MD) and molecular docking. Kinetic results showed that the two porphyrins are non-competitive inhibitors. Increasing pH, increases KI and cationic porphyrin has a higher KI and lower binding constant (Kb) at all pH ranges. Analyzing the secondary structure revealed that both ligands decrease the secondary structure and that the anionic porphyrin is more effective.