Pyridoxal is a pyridinecarbaldehyde and a form of vitamin B 6 which is converted to pyridoxal phosphate. Pyridoxal 5'-phosphate is involved in a wide range of biochemical reactions, including the metabolism of amino acids and glycogen, the synthesis of nucleic acids, hemoglobin, sphingomyelin, and other sphingolipids, and the synthesis of the neurotransmitters serotonin, dopamine, norepinephrine and gamma-aminobutyric acid (GABA). Pyridoxal is one of the natural forms available of vitamin B6, therefore, it is used for nutritional supplementation and for treating dietary shortage or imbalances. Some medically relevant bacteria, such as those in the genera Granulicatella and Abiotrophia, require pyridoxal for growth. This nutritional requirement can lead to the culture phenomenon of satellite growth. In in vitro culture, these pyridoxal-dependent bacteria may only grow in areas surrounding colonies of bacteria from other genera ("satellitism") that are capable of producing pyridoxal.

Orotic acid is a minor dietary constituent. Historically it was believed to be part of the vitamin B complex and was called vitamin B13, but it is now known that it is not a vitamin and is synthesized in the body, where it arises as an intermediate in the pathway for the synthesis of pyrimidine nucleotides. Orotic acid is converted to UMP by UMP synthase, a multifunctional protein with both orotate phosphoribosyl transferase and orotidylate decarboxylase activity. The most frequently observed inborn error of pyrimidine nucleotide synthesis is a mutation of the multifunctional protein UMP synthase. As a result, plasma orotic acid accumulates to high concentrations, and increased quantities appear in the urine. Orotic acid levels are elevated in the urea cycle defects ornithine transcarbamylase (OTC) deficiency, citrullinemia and argininosuccinic acidemia, as well as the mitochondrial transport disorder hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome. Orotic acid is also elevated in hereditary orotic aciduria, or uridine monophosphate synthase deficiency, an autosomal recessive disorder characterized by megaloblastic anemia and crystalluria. In addition, orotic acid in combination with leflunomide is in the phase II of clinical trial to evaluate the clinical efficacy and safety of a combination in kidney transplant patients with high levels of Polyoma BK viruria for the purpose of preventing polyoma BK viremia and nephropathy, that could lead to kidney transplant loss from viral damage, acute rejection or both.

Orotic acid is a minor dietary constituent. Historically it was believed to be part of the vitamin B complex and was called vitamin B13, but it is now known that it is not a vitamin and is synthesized in the body, where it arises as an intermediate in the pathway for the synthesis of pyrimidine nucleotides. Orotic acid is converted to UMP by UMP synthase, a multifunctional protein with both orotate phosphoribosyl transferase and orotidylate decarboxylase activity. The most frequently observed inborn error of pyrimidine nucleotide synthesis is a mutation of the multifunctional protein UMP synthase. As a result, plasma orotic acid accumulates to high concentrations, and increased quantities appear in the urine. Orotic acid levels are elevated in the urea cycle defects ornithine transcarbamylase (OTC) deficiency, citrullinemia and argininosuccinic acidemia, as well as the mitochondrial transport disorder hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome. Orotic acid is also elevated in hereditary orotic aciduria, or uridine monophosphate synthase deficiency, an autosomal recessive disorder characterized by megaloblastic anemia and crystalluria. In addition, orotic acid in combination with leflunomide is in the phase II of clinical trial to evaluate the clinical efficacy and safety of a combination in kidney transplant patients with high levels of Polyoma BK viruria for the purpose of preventing polyoma BK viremia and nephropathy, that could lead to kidney transplant loss from viral damage, acute rejection or both.

Orotic acid is a minor dietary constituent. Historically it was believed to be part of the vitamin B complex and was called vitamin B13, but it is now known that it is not a vitamin and is synthesized in the body, where it arises as an intermediate in the pathway for the synthesis of pyrimidine nucleotides. Orotic acid is converted to UMP by UMP synthase, a multifunctional protein with both orotate phosphoribosyl transferase and orotidylate decarboxylase activity. The most frequently observed inborn error of pyrimidine nucleotide synthesis is a mutation of the multifunctional protein UMP synthase. As a result, plasma orotic acid accumulates to high concentrations, and increased quantities appear in the urine. Orotic acid levels are elevated in the urea cycle defects ornithine transcarbamylase (OTC) deficiency, citrullinemia and argininosuccinic acidemia, as well as the mitochondrial transport disorder hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome. Orotic acid is also elevated in hereditary orotic aciduria, or uridine monophosphate synthase deficiency, an autosomal recessive disorder characterized by megaloblastic anemia and crystalluria. In addition, orotic acid in combination with leflunomide is in the phase II of clinical trial to evaluate the clinical efficacy and safety of a combination in kidney transplant patients with high levels of Polyoma BK viruria for the purpose of preventing polyoma BK viremia and nephropathy, that could lead to kidney transplant loss from viral damage, acute rejection or both.

Orotic acid is a minor dietary constituent. Historically it was believed to be part of the vitamin B complex and was called vitamin B13, but it is now known that it is not a vitamin and is synthesized in the body, where it arises as an intermediate in the pathway for the synthesis of pyrimidine nucleotides. Orotic acid is converted to UMP by UMP synthase, a multifunctional protein with both orotate phosphoribosyl transferase and orotidylate decarboxylase activity. The most frequently observed inborn error of pyrimidine nucleotide synthesis is a mutation of the multifunctional protein UMP synthase. As a result, plasma orotic acid accumulates to high concentrations, and increased quantities appear in the urine. Orotic acid levels are elevated in the urea cycle defects ornithine transcarbamylase (OTC) deficiency, citrullinemia and argininosuccinic acidemia, as well as the mitochondrial transport disorder hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome. Orotic acid is also elevated in hereditary orotic aciduria, or uridine monophosphate synthase deficiency, an autosomal recessive disorder characterized by megaloblastic anemia and crystalluria. In addition, orotic acid in combination with leflunomide is in the phase II of clinical trial to evaluate the clinical efficacy and safety of a combination in kidney transplant patients with high levels of Polyoma BK viruria for the purpose of preventing polyoma BK viremia and nephropathy, that could lead to kidney transplant loss from viral damage, acute rejection or both.

Orotic acid is a minor dietary constituent. Historically it was believed to be part of the vitamin B complex and was called vitamin B13, but it is now known that it is not a vitamin and is synthesized in the body, where it arises as an intermediate in the pathway for the synthesis of pyrimidine nucleotides. Orotic acid is converted to UMP by UMP synthase, a multifunctional protein with both orotate phosphoribosyl transferase and orotidylate decarboxylase activity. The most frequently observed inborn error of pyrimidine nucleotide synthesis is a mutation of the multifunctional protein UMP synthase. As a result, plasma orotic acid accumulates to high concentrations, and increased quantities appear in the urine. Orotic acid levels are elevated in the urea cycle defects ornithine transcarbamylase (OTC) deficiency, citrullinemia and argininosuccinic acidemia, as well as the mitochondrial transport disorder hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome. Orotic acid is also elevated in hereditary orotic aciduria, or uridine monophosphate synthase deficiency, an autosomal recessive disorder characterized by megaloblastic anemia and crystalluria. In addition, orotic acid in combination with leflunomide is in the phase II of clinical trial to evaluate the clinical efficacy and safety of a combination in kidney transplant patients with high levels of Polyoma BK viruria for the purpose of preventing polyoma BK viremia and nephropathy, that could lead to kidney transplant loss from viral damage, acute rejection or both.