Neopterin, Dihydroneopterin, Tetrahydroneopterin: Different Structures-Increasing Capacity Cleaving the Porphyrin in Heme Proteins

Abstract

Neopterin, 7,8-dihydroneopterin and 5,6,7,8-terahydroneopterm are secreted by human macrophages after activation by interferon-γ. The biological stability of the reduced pterins is less than one hour and therefore distinctly lower than that of neopterin. Ptendme derivatives are known to act as enhancers as well as scavengers of radical mediated processes. The effects of the three pteridines were investigated on hemoglobin and myoglobin, biomolecules that generate reactive oxygen species themselves. The amounts of liberated carbon monoxide and non heme iron stemming from the cleaved porphyrin were quantified. Iron and carbon monoxide were yielded at equimolar concentrations with a con-elation coefficients greater 0.9. Dihydroneopterin and tetrahydroneopterin were assumed to reduce the heme iron in intact heme molecules creating the conditions for adducting carbon monoxide and additionally the subsequent generation of hydroxide radicals via autooxidation. The effect of neopterin under these experimental concentrations was rather weak.

Keywords

• neopterin
• 7,8-dihydroneopterin
• 5,6,7,8-tetrahydroneopterin
• hemoglobin
• myoglobin
• porphyrin cleavage