Catabolic conversion of sepiapterin to 6-(1-carboxyethoxy)pterin by Bacillus subtilis

Structural elucidation of an intensely blue fluorescent compound (A) formed from sepiapterin by Bacillus subtilis is described. The structure of the catabolite (A) was found to be 2-amino-6-(1-carboxyethoxy)-4(3H)-pteridinone (9) from both spectroscopic and degradation studies. This was confirmed by an unambiguous synthesis of 9. The stereochemical structure of the side chain at the 6-position of A was confirmed to be the L(or S) configuration, as in sepiapterin, by analysis of the lactic acid formed from A on acid hydrolysis. This suggests that the side chain is rearranged intact during the catabolic conversion of sepiapterin. A possible mechanism for the conversion is discussed.