Reaction catalyzed by 6,7-dihydropteridine reductase (1.5.1.34)

		+		NAD(P)H	=			+		NAD(P)+
	quinonoid dihydro-L-threo-neopterin	+		NAD(P)H	=		tetrahydro-L-threo-neopterin	+		NAD(P)+