Browsing Pathways

The degradation of N-acetylneuraminate begins with its incorporation into the cytosol through a hydrogen symporter. Once inside the cytosol it is degraded by a N-acetylneuraminate lyase resulting in a release of a pyruvic acid and N-acetymannosamine. The latter compound is phosphorylated by an ATP driven N-Acetylmannosamine kinase resulting in the release of an ADP, a hydrogen ion and a N-Acetyl-D-mannosamine 6-phosphate. This phosphorylated compound is then metabolized by a putative N-acetylmannosamine-6-phosphate 2-epimerase resulting in the release of a N-Acetyl-D-glucosamine 6-phosphate. This compound is then deacetylated through a N-acetylglucosamine-6-phosphate deacetylase resulting in the release of an Acetic acid and a glucosamine 6-phosphate This compound can then be deaminated through a glucosamine-6-phosphate deaminase resulting in the release of an ammonium and a beta-D-fructofuranose 6-phosphate which can then be incorporated into the glycolysis pathway.

Spermidine is formed from decarboxy-SAM and putrescine by catalyzing spermidine synthase (also knowns as polyamine aminopropyltransferase). The source of putrescine is transported from outside of cell by putrescine/spermidine ABC transporter. Decarboxy-SAM comes from S-Adenosylmethionine with catalyzation of adenosylmethionine decarboxylase and cofactors: pyruvic acid and magnesium. The other product of the aminopropyltransferase reaction is S-methyl-5'-thioadenosine (MTA), which can be recycled back to L-methionine in many organisms, but not in E. coli. Inhibition of E. coli adenosylmethionine decarboxylase by spermidine appears to be the most significant regulator of polyamine biosynthesis, probably limiting it when the intracellular spermidine concentration becomes excessive. In E. coli most intracellular spermidine is bound to nucleic acids and phospholipids. (EcoCyc)

Aminopropylcadaverine, a polyamine, is the final product of aminopropylcadaverine biosynthesis pathway. Polyamines are involved in protein synthesis, DNA and RNA related processes, as well as the facilitation of cell stress resistance and membrane integrity; therefore polyamines are essential for cell growth. In this pathway, L-lysine is produced by lysine biosynthesis, then lysine decarboxylase will convert L-lysine into cadaverine. In the final step, spermidine synthase will catalyze cadaverine and decarboxy-SAM to aminopropylcadaverine as well as 5'-Methylthioadenosine.

L-Carnitine can stimulate anaerobic growth of E.coli when exogenous electron acceptors (i.e. nitrate, etc.) are absent. During anaerobic growth, E.coli can reduce L-carnitine to γ-butyrobetaine by CoA-linked intermediates when carbon and nitrogen are present in the system. Therefore, L-carnitine may act as external electron acceptor for anaerobic growth as well as generation of an osmoprotectant for cell.

Diacetylchitobiose (also known as N,N'-diacetylchitobiose and chitobiose) is a sole source of carbon for E.coli. PTS system mannitol-specific EIICBA component facilitates the imports of diacetylchitobiose as well as the phosphorylation to diacetylchitobiose 6'-phosphate. Later on, diacetylchitobiose 6'-phosphate is hydrolyzed to N-monoacetylchitobiose 6'-phosphate, which also produce acetic acid. N-monoacetylchitobiose 6'-phosphate undergoes further hydrolyzation to form N-Acetyl-D-Glucosamine 6-Phosphate and glucosamine by monoacetylchitobiose-6-phosphate hydrolase.

The degradation of N-acetylneuraminate begins with its incorporation into the cytosol through a hydrogen symporter. Once inside the cytosol it is degraded by a N-acetylneuraminate lyase resulting in a release of a pyruvic acid and N-acetymannosamine. The latter compound is phosphorylated by an ATP driven N-Acetylmannosamine kinase resulting in the release of an ADP, a hydrogen ion and a N-Acetyl-D-mannosamine 6-phosphate. This phosphorylated compound is then metabolized by a putative N-acetylmannosamine-6-phosphate 2-epimerase resulting in the release of a N-Acetyl-D-glucosamine 6-phosphate. This compound is then deacetylated through a N-acetylglucosamine-6-phosphate deacetylase resulting in the release of an Acetic acid and a glucosamine 6-phosphate This compound can then be deaminated through a glucosamine-6-phosphate deaminase resulting in the release of an ammonium and a beta-D-fructofuranose 6-phosphate which can then be incorporated into the glycolysis pathway.

This pathway demonstrates the biosynthesis of tetrahydromonapterin in E.coli. However, it is still unclear about biological role of tetrahydromonapterin. GTP cyclohydrolase 1 generates formic acid and 7,8-dihydroneopterin 3'-triphosphate with cofactor GTP and water. 7,8-dihydroneopterin 3'-triphosphate is converted to dihydromonapterin-triphosphate by d-erythro-7,8-dihydroneopterin triphosphate epimerase (folX). Later, dihydromonapterin-triphosphate is hydroxylated to dihydromethysticin, and eventually form tetrahydromonapterin via dihydromonapterin reductase (folM) with cofactor NADPH.

Aminopropylcadaverine, a polyamine, is the final product of aminopropylcadaverine biosynthesis pathway. Polyamines are involved in protein synthesis, DNA and RNA related processes, as well as the facilitation of cell stress resistance and membrane integrity; therefore polyamines are essential for cell growth. In this pathway, L-lysine is produced by lysine biosynthesis, then lysine decarboxylase will convert L-lysine into cadaverine. In the final step, spermidine synthase will catalyze cadaverine and decarboxy-SAM to aminopropylcadaverine as well as 5'-Methylthioadenosine.

Spermidine is formed from decarboxy-SAM and putrescine by catalyzing spermidine synthase (also knowns as polyamine aminopropyltransferase). The source of putrescine is transported from outside of cell by putrescine/spermidine ABC transporter. Decarboxy-SAM comes from S-Adenosylmethionine with catalyzation of adenosylmethionine decarboxylase and cofactors: pyruvic acid and magnesium. The other product of the aminopropyltransferase reaction is S-methyl-5'-thioadenosine (MTA), which can be recycled back to L-methionine in many organisms, but not in E. coli. Inhibition of E. coli adenosylmethionine decarboxylase by spermidine appears to be the most significant regulator of polyamine biosynthesis, probably limiting it when the intracellular spermidine concentration becomes excessive. In E. coli most intracellular spermidine is bound to nucleic acids and phospholipids. (EcoCyc)

The degradation of N-acetylneuraminate begins with its incorporation into the cytosol through a hydrogen symporter. Once inside the cytosol it is degraded by a N-acetylneuraminate lyase resulting in a release of a pyruvic acid and N-acetymannosamine. The latter compound is phosphorylated by an ATP driven N-Acetylmannosamine kinase resulting in the release of an ADP, a hydrogen ion and a N-Acetyl-D-mannosamine 6-phosphate. This phosphorylated compound is then metabolized by a putative N-acetylmannosamine-6-phosphate 2-epimerase resulting in the release of a N-Acetyl-D-glucosamine 6-phosphate. This compound is then deacetylated through a N-acetylglucosamine-6-phosphate deacetylase resulting in the release of an Acetic acid and a glucosamine 6-phosphate This compound can then be deaminated through a glucosamine-6-phosphate deaminase resulting in the release of an ammonium and a beta-D-fructofuranose 6-phosphate which can then be incorporated into the glycolysis pathway.