THE ASSOCIATION AND ACTIVITIES OF PTERIDINES IN PHOTOSYNTHETIC SYSTEMS*^,†

Abstract

Unconjugated pteridines are associated with the photosynthetic systems of several organisms. Inhibition of the development of the photosynthetic system of Rhodospirillum rubrum with the pteridine inhibitor 4-phenoxy-2,6-diamino pyridine (PDAP) is reversed by biopterin, a natural pteridine. Evidence is presented which indicates an electron transport function for pteridines. Specific interaction of reduced pteridines with isolated pigment protein complexes, leading to red-shifted absorption bands, has suggested a mechanism for photochemical energy trapping.

Photoinduced Formation of Reactive Oxygen Species from the Acid Form of 6‐(Hydroxymethyl)pterin in Aqueous Solution

“…TLC Experiments were performed on DEAE cellulose plates (100 mm) eluting with 0.3% aq. NH 4 Cl soln. Irradiated HPT (1) solns.…”

“…-Pterins, i.e., 2-amino-4-hydroxypteridine derivatives, occur in a wide range of biological systems [1] [2]. Although pterins are present in only minute amounts in living systems, they are known to participate in important biological functions [1 -3] including various photobiological processes such as photoreception in plants [4] [5]. For example, the folic acid derivative '5,10-methenyltetrahydrofolate' is present as the light-harvesting antenna in DNA photolyases [6] [7], which, in turn, are involved in DNA repair after UV irradiation.…”

Production and quenching of reactive oxygen species by pterin derivatives, an intriguing class of biomolecules

“…The folic acid derivative 5,10-methenyltetrahydrofolate is present as the light-harvesting antenna in DNA photolyases [16], involved in DNA repair after UV irradiation. Some reports suggested that pterins may act as blue antennas in superior plants [17] and play some role in photosynthesis [18].…”

Generation of Reactive Oxygen Species during the Photolysis of 6‐(Hydroxymethyl)pterin in Alkaline Aqueous Solutions

“…A derivative of folic acid, a conjugated pterin, is the light-harvesting chromophore of DNA photolyases [6] [7], enzymes involved in DNA repair processes that take place after UV irradiation. It has been suggested that pterins may play some role in photosynthesis [8], and they have been found in photosensitive organs such as the eyes of different animals [9]. Pterins are also interesting as possible photosensitizers in photochemical processes that take place in organisms exposed to UV-A radiation; e.g., pterins act as sensitizers in photochemical reactions that induce DNA damage [10] [11] and are able to generate singlet oxygen ( 1 O 2 ) [12] [13].…”