Pterins biological activity

In addition to direct trafficking to target metalloproteins, some metals need to enter specialized biosynthetic pathways for metal cofactor assembly. For example, iron in metaUoenzymes is usually present as part of heme or Fe-S clusters, so it must be routed into the biosynthetic pathways for these cofactors. In a similar vein, molybdenum is not biologically active unless it is first incorporated with a pterin compound to form molybdenum... 

Aiello, A., Fattorusso, E., Magno, S., Misuraca, G., and Novellino, E. (1987a) 2-Amino-6(14R,2 S)-l, 2 -dihydroxypropyl-3methyl-pterin-4-one, a biologically active metabolite from the anthozoan Astroides calycularis Pallas. Experientia, 43, 950-952. 

Pteridines are widely distributed in nature and function as pigments, biological markers, and cofactors of enzymatic reactions. The oxidized heteroaromatic forms show a characteristic fluorescence which allows easy detection even in low concentrations. However, the more active 5,6,7,8-tetrahydro derivatives are nonfluorescing and oxidizable and create experimental problems in handling this type of compound. So far, all naturally occurring pteridines have turned out to be derivatives of pterin (2) and lumazine (3) which are modified by different substituents and functional groups in the 6- and/or 7-position. 

The molybdenum cofactor (Moco) is an extraordinary molecule in biology. As a small metal-containing compound, it has the unprecedented combination of a dithiolene chelate for metal binding and a pterin appended to a pyran ring. The resultant cofactor is electronically nimble due to the presence of three redox active moieties, ie. the molybdenum atom, the dithiolene and the pterin, which in concert can support a range of redox events. 

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