Figure 3.

Metabolic links between His and Trp, purine, pyrimidine and pyridine nucleotide metabolism. Red arrows indicate the pathway of His biosynthesis, dark blue the de novo (solid line) and salvage (dotted line) pathways of purine biosynthesis, light blue the de novo (solid line) and salvage (dotted line) pathways of pyrimidine biosynthesis, green the pyridine nucleotide biosynthetic pathway, and brown the Trp biosynthetic pathway. For clarity only selected metabolic intermediates have been shown. Abbreviations used are: AICAR (5′-phosphoribosyl-4-carboximide-5-aminoimidazole), AMP (adenosine monophosphate), ATP (adenosine triphosphate), CTP (cytosine triphosphate), GMP (guanosine monophosphate), IGP (imidazole glycerol-phosphate), IMP (inosine monophosphate), NAD+ (nicotinamide adenine dinucleotide), NADP+ (nicotinamide adenine dinucleotide phosphate) NAM (nicotinic acid mononucleotide), PRPP (5′-phosphoribosyl-1-pyrophosphate), UMP (uridine monophosphate) and UTP (uridine triphosphate).