Photooxidation of tetrahydrobiopterin under UV irradiation: possible pathways and mechanisms.

Tetrahydrobiopterin (H4 Bip) is a cofactor for several key enzymes, including NO synthases and aromatic amino acid hydroxylases (AAHs). Normal functioning of the H4 Bip regeneration cycle is extremely important for the work of AAHs. Oxidized pterins may accumulate if the H4 Bip regeneration cycle is disrupted or if H4 Bip autoxidation occurs.

Excited flavin and pterin coenzyme molecules in evolution.

Excited flavin and pterin molecules are active in intermolecular energy transfer and in photocatalysis of redox reactions resulting in conservation of free energy. Flavin-containing pigments produced in models of the prebiotic environment are capable of converting photon energy into the energy of phosphoanhydride bonds of ATP. However, during evolution photochemical reactions involving excited FMN or FAD molecules failed to become participants of bioenergy transfer systems, but they appear in enzymes responsible for repair of UV-damaged DNA (DNA photolyases) and also in receptors of blue and UV-A light regulating vital functions of organisms.

Abiogenic photophosphorylation of ADP to ATP sensitized by flavoproteinoid microspheres.

A model for abiogenic photophosphorylation of ADP by orthophosphate to yield ATP was studied. The model is based on the photochemical activity of flavoproteinoid microspheres that are formed by aggregation in an aqueous medium of products of thermal condensation of a glutamic acid, glycine and lysine mixture (8:3:1) and contain, along with amino acid polymers (proteinoids), abiogenic isoalloxazine (flavin) pigments. Irradiation of aqueous suspensions of microspheres with blue visible light or ultraviolet in the presence of ADP and orthophosphate resulted in ATP formation.