| Metabolism and Physiological Effects of Indoxyl glucuronide |  | Metabolic | Tryptophan / Indole |
| Metabolism and Physiological Effects of Indoxyl Sulfate |  | Metabolic | Tryptophan / Mesoheme / Indole / Indoxyl sulfate |
| Metabolism and Physiological Effects of Isovalerylglycine |  | Metabolic | Glycine / Proline |
| Metabolism and Physiological Effects of Kynurenic Acid |  | Metabolic | Pyridoxal phosphate / Tryptophan / Kynurenine / Mesoheme |
| Metabolism and Physiological Effects of Kynurenine |  | Disease | Tryptophan / Formic acid / Kynurenine / Mesoheme |
| Metabolism and Physiological Effects of N-Acetyl-1-Methylhistidine |  | Metabolic | Histidine / Ademetionine / 1-Methylhistidine |
| Metabolism and Physiological Effects of N-Acetyl-3-Methylhistidine |  | Metabolic | Histidine / Ademetionine |
| Metabolism and Physiological Effects of N-Acetyl-L-Alanine |  | Metabolic | Alanine |
| Metabolism and Physiological Effects of N-Acetylhistidine |  | Metabolic | Histidine |
| Metabolism and Physiological Effects of N-Acetylmethionine |  | Metabolic | Methionine / N-Acetylmethionine |
| Metabolism and Physiological Effects of N-Acetylphenylalanine |  | Metabolic | Phenylalanine |
| Metabolism and Physiological Effects of N-Acetylproline |  | Metabolic | Proline / N-Acetylproline |
| Metabolism and Physiological Effects of N-Acetylserine |  | Metabolic | Serine / N-Acetyl-Serine |
| Metabolism and Physiological Effects of N-Acetylthreonine |  | Metabolic | Threonine |
| Metabolism and Physiological Effects of N-Acetyltryptophan |  | Metabolic | Tryptophan |
| Metabolism and Physiological Effects of N-Acetylvaline |  | Metabolic | Valine |
| Metabolism and Physiological Effects of N-alpha-Acetyl-L-arginine |  | Metabolic | Pyridoxal phosphate / Arginine / Aspartic acid / Ornithine / L-Glutamine / Adenosine phosphate / Glutamic acid / Citrulline / ATP / Calcium / N-acetyl-L-arginine / Oxogluric acid / Glutaric Acid / Urea / Pyrophosphoric acid / Maleic acid |
| Metabolism and Physiological Effects of N-Formyl-L-Methionine |  | Metabolic | Adenosine phosphate / Methionine / ATP / N-Acetylmethionine / Pyrophosphoric acid |
| Metabolism and Physiological Effects of O-Sulfotyrosine |  | Metabolic | Phenylalanine / Tyrosine / Sapropterin / Iron |
| Metabolism and Physiological Effects of Orotic acid |  | Metabolic | Aspartic acid / L-Glutamine / ATP / Zinc / Flavin mononucleotide |
| Metabolism and Physiological Effects of Oxalic acid |  | Metabolic | Pyridoxal phosphate / Ascorbic acid / Succinic acid / Glutamic acid / Glycine / Proline / Oxogluric acid / Flavin adenine dinucleotide / Oxalic Acid / Glyoxylic acid |
| Metabolism and Physiological Effects of p-Cresol sulphate |  | Metabolic | Pyridoxal phosphate / Tyrosine / Glutamic acid / P-Cresol / Oxogluric acid / 4-Hydroxyphenylpyruvic acid |
| Metabolism and Physiological Effects of Para-cresol |  | Metabolic | Pyridoxal phosphate / Tyrosine / Glutamic acid / P-Cresol / Oxogluric acid / 4-Hydroxyphenylpyruvic acid |
| Metabolism and Physiological Effects of Para-cresyl glucuronide |  | Metabolic | Tyrosine / P-Cresol / 4-Hydroxyphenylpyruvic acid |
| Metabolism and Physiological Effects of Phenol |  | Metabolic | Tyrosine / Phenol |