Browsing Pathways

This pathway is a compilation of Escherichia coli inner membrane transport complexes that transport compounds from the periplasmic space into the cytosol. Many compound classes are carried by these inner membrane transport complexes including sugars, amino acids, and lipids.

The metabolism of L-arginine starts with the acetylation of L-glutamic acid resulting in a N-acetylglutamic acid while releasing a coenzyme A and a hydrogen ion. N-acetylglutamic acid is then phosphorylated via an ATP driven acetylglutamate kinase which yields a N-acetyl-L-glutamyl 5-phosphate. This compound undergoes a NDPH dependent reduction resulting in N-acetyl-L-glutamate 5-semialdehyde, which then reacts with L-glutamic acid through a acetylornithine aminotransferase / N-succinyldiaminopimelate aminotransferase to produce an N-acetylornithine. Next N-acetylornithine is deacetylated through a acetylornithine deacetylase yielding an ornithine. L-glutamine is used to synthesize carbamoyl phosphate through the interaction of L-glutamine, water, ATP, and hydrogen carbonate. This reaction yields ADP, L-glutamic acid, phosphate, and hydrogen ion. Carbamoyl phosphate and ornithine are used to catalyze the production of citrulline through an ornithine carbamoyltransferase. Citrulline reacts with L-aspartic acid through an ATP dependent enzyme, argininosuccinate synthase to produce pyrophosphate, AMP and argininosuccinic acid. Argininosussinic acid is then lyase to produce L-arginine and fumaric acid. L-arginine can be metabolized into succinic acid by two different sets of reactions: 1. Arginine reacts with succinyl-CoA through a arginine N-succinyltransferase resulting in N2-succinyl-L-arginine while releasing CoA and Hydrogen Ion. N2-succinyl-L-arginine is then dihydrolase to produce a N2-succinyl-L-ornithine through a N-succinylarginine dihydrolase which in turn reacts with oxoglutaric acid through succinylornithine transaminase resulting in L-glutamic acid and N2-succinyl-L-glutamic acid 5-semialdehyde. Next N2-succinyl-L-glutamic acid 5-semialdehyde reacts with a NAD dependent dehydrogenase resulting in N2-succinylglutamate and releases NADH and hydrogen ion. Finally, N2-succinylglutamate reacts with water through a succinylglutamate desuccinylase resulting in L-glutamic acid and a succinic acid. The succinic acid is then incorporated in the TCA cycle 2. Argine reacts with carbon dioxide and a hydrogen ion through a biodegradative arginine decarboxylase, resulting in Agmatine. Agmatine is transformed into putrescine by reacting with water and an agmatinase, and releasing urea. Putrescine can be metabolized by reaction with either l-glutamic acid or oxoglutaric acid. If putrescine reacts with L-glutamic acid, it reacts through an ATP mediated gamma-glutamylputrescine producing a hydrogen ion, ADP, phosphate and gamma-glutamyl-L-putrescine. Gamma-glutamyl-L-putrescine is reduced via interactions with oxygen, water and a gamma-glutamylputrescine oxidoreductase resulting in ammonium, hydrogen peroxide and 4-gamma-glutamylamino butanal. Dehydrogenated through a NADP mediated reaction lead by gamma-glutamyl-gamma-aminobutaryaldehyde dehydrogenase, 4-gamma-glutamylamino butanal is converted into hydrogen ions, NADPH and 4-glutamylamino butanoate. In turn, the latter compound reacts with water through a gamma-glutamyl-gamma-aminobutyrate hydrolase resulting in L-glutamic acid and Gamma aminobutyric acid. On the other hand, if putrescine reacts with oxoglutaric acid through a putrescine aminotransferase, it results in L-glutamic acid, and a 4-aminobutyraldehyde, which continues and reacts with water through a NAD dependent gamma aminobutyraldehyde dehydrogenase resulting in hydrogen ion, NADH and gamma-aminobutyric acid. Gamma Aaminobutyric acid reacts with oxoglutaric acid through 4-aminobutyrate aminotransferase resulting in L-glutamic acid and succinic acid semialdehyde. Succinic acid semialdehyde then reacts with either NADP or NAD to produce succinic acid through succinate-semialdehyde dehydrogenase or aldehyde dehydrogenase-like protein yneI respectively. Succinic acid can then be integrated in the TCA cycle.

Fructose metabolism begins with the transport of beta-D-glucose 6-phosphate through a glucose PTS permease. This compound is isomerized by a glucose-6-phosphate isomerase resulting in fructose 6-phosphate. This compound can be phosphorylated by two different enzymes: a pyridoxal phosphatase/fructose 1,6-bisphosphatase or an ATP-driven 6-phosphofructokinase-1, resulting in fructose 1,6-biphosphate. This compound can either react with a fructose bisphosphate aldolase class 1 resulting in D-glyceraldehyde 3-phosphate and dihydroxyacetone phosphate or through a fructose biphosphate aldolase class 2 resulting in D-glyceraldehyde 3-phosphate. This compound can then either react in a reversible triosephosphate isomerase resulting in dihydroxyacetone phosphate or react with a phosphate through an NAD-dependent glyceraldehyde 3-phosphate dehydrogenase resulting in glyceric acid 1,3-biphosphate. This compound is dephosphorylated by a phosphoglycerate kinase resulting in 3-phosphoglyceric acid. This compound, in turn, can either react with a 2,3-bisphosphoglycerate-independent phosphoglycerate mutase or a 2,3-bisphosphoglycerate-independent phosphoglycerate mutase resulting in 2-phospho-D-glyceric acid. This compound interacts with an enolase resulting in a phosphoenolpyruvic acid and water. Phosphoenolpyruvic acid can react either through an AMP-driven phosphoenoylpyruvate synthase or an ADP-driven pyruvate kinase protein complex resulting in pyruvic acid. The pyruvic acid reacts with CoA through an NAD-driven pyruvate dehydrogenase complex resulting in carbon dioxide and an acetyl-CoA which gets incorporated into the TCA cycle pathway.

Vitamin B6 metabolism in bacteria involves the biosynthesis and utilization of various forms of Vitamin B6, primarily pyridoxal 5'-phosphate (PLP), the active form of the vitamin. Bacteria can synthesize Vitamin B6 through two main pathways: the de novo DXP-independent pathway (pyridoxal phosphate biosynthesis I) and the DXP-dependent pathway. In the de novo pathway, key enzymes like Pdx1 and Pdx2 convert intermediates into pyridoxine 5'-phosphate (PNP), which is then oxidized to PLP by the enzyme pyridoxine phosphate oxidase (PdxH). PLP acts as a cofactor for various enzymes involved in amino acid metabolism, including transaminases, decarboxylases, and racemases.Bacteria rely on PLP for critical cellular processes, including amino acid metabolism, stress response, and protection against oxidative damage.

Fatty acid oxidation is also known as beta-oxidation. Fatty acids are an important energy source because they are anhydrous and can be reduced. Fatty acids are good sources of energy as they yield more energy than carbohydrates. The fatty acid oxidation pathway degrades fatty acids into acetyl-CoA under anaerobic and aerobic conditions. Enzymes of this pathway can process short and long chain fatty acids. The first step in the pathway is the conversion of acyl-CoA to enoyl-CoA. The pathway continues in a cycle, each turn removing two carbon atoms from the input acyl-CoA to produce acetyl-CoA. Each turn also produces NADH.

The reaction of pyruvate to cytochrome bd terminal oxidase electron transfer starts with 2 pyruvate and 2 water molecules reacting in a pyruvate oxidase resulting in the release of 4 electrons into the inner membrane, and releasing 2 carbon dioxide molecules , 2 acetate and 4 hydrogen ion into the cytosol. 2 ubiquinone,4 hydrogen ion and 4 electron ion react resulting in the release of 2 ubiquinol . The 2 ubiquinol in turn release 4 hydrogen ions into the periplasmic space through a cytochrome bd-I terminal oxidase and releasing 4 electrons through the enzyme. Oxygen and 4 hydrogen ion reacts with the 4 electrons resulting in 2 water molecules.