1.13.11.11	D-tryptophan + O2	low activity	
1.13.11.11	L-tryptophan + O2	-	
1.13.11.11	additional information	in mouse liver homogenate, TDO activity is five times lower for D-Trp than that for L-Trp. L-Trp is the preferred substrate for nicotinamide synthesis because L-Trp metabolism is more efficient than D-Trp in mice