Browsing Pathways

The biosynthesis of threonine starts with oxalacetic acid interacting with an L-glutamic acid through an aspartate aminotransferase resulting in a oxoglutaric acid and an L-aspartic acid. The latter compound is then phosphorylated by an ATP driven Aspartate kinase resulting in an a release of an ADP and an L-aspartyl-4-phosphate. L-aspartyl-4-phosphate then interacts with a hydrogen ion through an NADPH driven aspartate semialdehyde dehydrogenase resulting in the release of a phosphate, an NADP and a L-aspartate-semialdehyde. The latter compound interacts with a hydrogen ion through a NADPH driven aspartate kinase / homoserine dehydrogenase resulting in the release of an NADP and a L-homoserine. L-homoserine is phosphorylated through an ATP driven homoserine kinase resulting in the release of an ADP, a hydrogen ion and a O-phosphohomoserine. O-phosphohomoserine then interacts with a water molecule and threonine synthase resulting in the release of a phosphate and an L-threonine.

Cardiolipin (CL) is an important component of the inner mitochondrial membrane where it constitutes about 20% of the total lipid composition. It is essential for the optimal function of numerous enzymes that are involved in mitochondrial energy metabolism (Wikipedia). Cardiolipin biosynthesis occurs mainly in the mitochondria, but there also exists an alternative synthesis route for CDP-diacylglycerol that takes place in the endoplasmic reticulum. This second route may supplement this pathway. All membrane-localized enzymes are coloured dark green in the image. First, dihydroxyacetone phosphate (or glycerone phosphate) from glycolysis is used by the cytosolic enzyme glycerol-3-phosphate dehydrogenase [NAD(+)] to synthesize sn-glycerol 3-phosphate. Second, the mitochondrial outer membrane enzyme glycerol-3-phosphate acyltransferase esterifies an acyl-group to the sn-1 position of sn-glycerol 3-phosphate to form 1-acyl-sn-glycerol 3-phosphate (lysophosphatidic acid or LPA). Third, the enzyme 1-acyl-sn-glycerol-3-phosphate acyltransferase converts LPA into phosphatidic acid (PA or 1,2-diacyl-sn-glycerol 3-phosphate) by esterifying an acyl-group to the sn-2 position of the glycerol backbone. PA is then transferred to the inner mitochondrial membrane to continue cardiolipin synthesis. Fourth, magnesium-dependent phosphatidate cytidylyltransferase catalyzes the conversion of PA into CDP-diacylglycerol. Fifth, CDP-diacylglycerol--glycerol-3-phosphate 3-phosphatidyltransferase synthesizes phosphatidylglycerophosphate (PGP). Sixth, phosphatidylglycerophosphatase and protein-tyrosine phosphatase dephosphorylates PGP to form phosphatidylglycerol (PG). Last, cardiolipin synthase catalyzes the synthesis of cardiolipin by transferring a phosphatidyl group from a second CDP-diacylglycerol to PG. It requires a divalent metal cation cofactor.

The biosynthesis of L-tryptophan begins with L-glutamine interacting with a chorismate through a anthranilate synthase which results in a L-glutamic acid, a pyruvic acid, a hydrogen ion and a 2-aminobenzoic acid. The aminobenzoic acid interacts with a phosphoribosyl pyrophosphate through an anthranilate synthase component II resulting in a pyrophosphate and a N-(5-phosphoribosyl)-anthranilate. The latter compound is then metabolized by an indole-3-glycerol phosphate synthase / phosphoribosylanthranilate isomerase resulting in a 1-(o-carboxyphenylamino)-1-deoxyribulose 5'-phosphate. This compound then interacts with a hydrogen ion through a indole-3-glycerol phosphate synthase / phosphoribosylanthranilate isomerase resulting in the release of carbon dioxide, a water molecule and a (1S,2R)-1-C-(indol-3-yl)glycerol 3-phosphate. The latter compound then interacts with a D-glyceraldehyde 3-phosphate and an Indole. The indole interacts with an L-serine through a tryptophan synthase, β subunit dimer resulting in a water molecule and an L-tryptophan. The metabolism of L-tryptophan starts with L-tryptophan being dehydrogenated by a tryptophanase / L-cysteine desulfhydrase resulting in the release of a hydrogen ion, an Indole and a 2-aminoacrylic acid. The latter compound is isomerized into a 2-iminopropanoate. This compound then interacts with a water molecule and a hydrogen ion spontaneously resulting in the release of an Ammonium and a pyruvic acid. The pyruvic acid then interacts with a coenzyme A through a NAD driven pyruvate dehydrogenase complex resulting in the release of a NADH, a carbon dioxide and an Acetyl-CoA

Cardiolipin (CL) is an important component of the inner mitochondrial membrane where it constitutes about 20% of the total lipid composition. It is essential for the optimal function of numerous enzymes that are involved in mitochondrial energy metabolism (Wikipedia). Cardiolipin biosynthesis occurs mainly in the mitochondria, but there also exists an alternative synthesis route for CDP-diacylglycerol that takes place in the endoplasmic reticulum. This second route may supplement this pathway. All membrane-localized enzymes are coloured dark green in the image. First, dihydroxyacetone phosphate (or glycerone phosphate) from glycolysis is used by the cytosolic enzyme glycerol-3-phosphate dehydrogenase [NAD(+)] to synthesize sn-glycerol 3-phosphate. Second, the mitochondrial outer membrane enzyme glycerol-3-phosphate acyltransferase esterifies an acyl-group to the sn-1 position of sn-glycerol 3-phosphate to form 1-acyl-sn-glycerol 3-phosphate (lysophosphatidic acid or LPA). Third, the enzyme 1-acyl-sn-glycerol-3-phosphate acyltransferase converts LPA into phosphatidic acid (PA or 1,2-diacyl-sn-glycerol 3-phosphate) by esterifying an acyl-group to the sn-2 position of the glycerol backbone. PA is then transferred to the inner mitochondrial membrane to continue cardiolipin synthesis. Fourth, magnesium-dependent phosphatidate cytidylyltransferase catalyzes the conversion of PA into CDP-diacylglycerol. Fifth, CDP-diacylglycerol--glycerol-3-phosphate 3-phosphatidyltransferase synthesizes phosphatidylglycerophosphate (PGP). Sixth, phosphatidylglycerophosphatase and protein-tyrosine phosphatase dephosphorylates PGP to form phosphatidylglycerol (PG). Last, cardiolipin synthase catalyzes the synthesis of cardiolipin by transferring a phosphatidyl group from a second CDP-diacylglycerol to PG. It requires a divalent metal cation cofactor.

E. coli lipid A is synthesized on the cytoplasmic surface of the inner membrane. Starting with either the fructose 6-phosphate produced by glycolysis and pyruvate dehydrogenase or obtained from the interaction with D-fructose interacting with a mannose PTS permease. Fructose 6-phosphate interacts with L-glutamine through a D-fructose-6-phosphate aminotransferase resulting into a L-glutamic acid and a glucosamine 6-phosphate. The latter compound is isomerized through a phosphoglucosamine mutase resulting a glucosamine 1-phosphate. This compound is acetylated, interacting with acetyl-CoA through a bifunctional protein glmU resulting in a Coenzyme A, hydrogen ion and N-acetyl-glucosamine 1-phosphate. The latter interacts with UTP and hydrogen ion through the bifunctional protein glmU resulting in a pyrophosphate and a UDP-N-acetylglucosamine. UDP-N-acetylglucosamine iinteracts with (3R)-3-hydroxymyristoyl-[acp] through an UDP-N-acetylglucosamine acyltransferase resulting in a holo-[acp] and a UDP-3-O[(3R)-3-hydroxymyristoyl]-N-acetyl-alpha-D-glucosamine. The latter continues and reacts with water through UDP-3-O-acyl-N-acetylglucosamine deacetylase resulting in an acetic acid and UDP-3-O-(3-hydroxymyristoyl)-α-D-glucosamine. The latter compound interacts with (3R)-3-hydroxymyristoyl-[acp] through UDP-3-O-(R-3-hydroxymyristoyl)-glucosamine N-acyltransferase releasing a hydrogen ion, a holo-acp and UDP-2-N,3-O-bis[(3R)-3-hydroxytetradecanoyl]-α-D-glucosamine. The latter compound is hydrolase by interacting with water and a UDP-2,3-diacylglucosamine hydrolase resulting in UMP, hydrogen ion and 2,3-bis[(3R)-3-hydroxymyristoyl]-α-D-glucosaminyl 1-phosphate. The latter interacts with a UDP-2-N,3-O-bis[(3R)-3-hydroxytetradecanoyl]-α-D-glucosamine through a lipid A disaccharide synthase resulting in a release of UDP, hydrogen ion and a lipid A disaccharide. The lipid A disaccharide is phosphorylated by an ATP mediated tetraacyldisaccharide 4'-kinase resulting in the release of hydrogen ion and lipid IVA. A D-ribulose 5-phosphate is isomerized with D-arabinose 5-phosphate isomerase 2 resulting in a D-arabinose 5-phosphate. D-arabinose 5-phosphate interacts with water and phosphoenolpyruvic acid through a 3-deoxy-D-manno-octulosonate 8-phosphate synthase resulting in the release of phosphate and 3-deoxy-D-manno-octulosonate 8-phosphate. This compound interacts with water through a 3-deoxy-D-manno-octulosonate 8-phosphate phosphatase thus releasing a phosphate and a 3-deoxy-D-manno-octulosonate. The latter compound interacts with CTP through a 3-deoxy-D-manno-octulosonate cytidylyltransferase resulting in a pyrophosphate and CMP-3-deoxy-α-D-manno-octulosonate. CMP-3-deoxy-α-D-manno-octulosonate and lipid IVA interact with each other through a KDO transferase resulting in CMP, hydrogen ion and alpha-Kdo-(2-->6)-lipid IVA. The latter compound reacts with CMP-3-deoxy-α-D-manno-octulosonate through a KDO transferase resulting in a CMP, hydrogen ion, and a a-Kdo-(2->4)-a-Kdo-(2->6)-lipid IVA. The latter compound can either react with a palmitoleoyl-acp through a palmitoleoyl acyltransferase resulting in the release of a holo-acyl carriere protein and a Kdo2-palmitoleoyl-lipid IVa which in turn reacts with a myristoyl-acp through a myristoyl-acp dependent acyltransferase resulting in a release of a holo-acp and a Kdo2-lipid A, cold adapted, or it can interact with a dodecanoyl-[acp] lauroyl acyltransferase resulting in a holo-[acp] and a (KDO)2-(lauroyl)-lipid IVA. The latter compound reacts with a myristoyl-[acp] through a myristoyl-acyl carrier protein (ACP)-dependent acyltransferase resulting in a holo-[acp], (KDO)2-lipid A. The latter compound reacts with ADP-L-glycero-beta-D-manno-heptose through ADP-heptose:LPS heptosyltransferase I resulting hydrogen ion, ADP, heptosyl-KDO2-lipid A. The latter compound interacts with ADP-L-glycero-beta-D-manno-heptose through ADP-heptose:LPS heptosyltransferase II resulting in ADP, hydrogen ion and (heptosyl)2-Kdo2-lipid A. The latter compound UDP-glucose interacts with (heptosyl)2-Kdo2-lipid A resulting in UDP, hydrogen ion and glucosyl-(heptosyl)2-Kdo2-lipid A. Glucosyl-(heptosyl)2-Kdo2-lipid A (Escherichia coli) is phosphorylated through an ATP-mediated lipopolysaccharide core heptose (I) kinase resulting in ADP, hydrogen ion and glucosyl-(heptosyl)2-Kdo2-lipid A-phosphate. The latter compound interacts with ADP-L-glycero-beta-D-manno-heptose through a lipopolysaccharide core heptosyl transferase III resulting in ADP, hydrogen ion, and glucosyl-(heptosyl)3-Kdo2-lipid A-phosphate. The latter compound is phosphorylated through an ATP-driven lipopolysaccharide core heptose (II) kinase resulting in ADP, hydrogen ion and glucosyl-(heptosyl)3-Kdo2-lipid A-bisphosphate. The latter compound interacts with UDP-alpha-D-galactose through a UDP-D-galactose:(glucosyl)lipopolysaccharide-1,6-D-galactosyltransferase resulting in a UDP, a hydrogen ion and a galactosyl-glucosyl-(heptosyl)3-Kdo2-lipid A-bisphosphate. The latter compound interacts with UDP-glucose through a (glucosyl)LPS α-1,3-glucosyltransferase resulting in a hydrogen ion, a UDP and galactosyl-(glucosyl)2-(heptosyl)3-Kdo2-lipid A-bisphosphate. This compound then interacts with UDP-glucose through a UDP-glucose:(glucosyl)LPS α-1,2-glucosyltransferase resulting in UDP, a hydrogen ion and galactosyl-(glucosyl)3-(heptosyl)3-Kdo2-lipid A-bisphosphate. This compound then interacts with ADP-L-glycero-beta-D-manno-heptose through a lipopolysaccharide core biosynthesis; heptosyl transferase IV; probably hexose transferase resulting in a Lipid A-core. A lipid A-core is then exported into the periplasmic space by a lipopolysaccharide ABC transporter. The lipid A-core is then flipped to the outer surface of the inner membrane by the ATP-binding cassette (ABC) transporter, MsbA. An additional integral membrane protein, YhjD, has recently been implicated in LPS export across the IM. The smallest LPS derivative that supports viability in E. coli is lipid IVA. However, it requires mutations in either MsbA or YhjD, to suppress the normally lethal consequence of an incomplete lipid A . Recent studies with deletion mutants implicate the periplasmic protein LptA, the cytosolic protein LptB, and the IM proteins LptC, LptF, and LptG in the subsequent transport of nascent LPS to the outer membrane (OM), where the LptD/LptE complex flips LPS to the outer surface.

Chorismate is an intermediate in tyrosine, phenylalanine and tryptophan synthesis and a precursor for folic acid, ubiquinone, enterochelin and menaquinone. Three enzymes catalyze the first step in chorismate biosynthesis. Synthesis may be reduced by feedback inhibition of tyrosine, phenylalanine and tryptophan to the enzymes. The biosynthesis of chorismate starts with D-Erythrose-4-phosphate getting transformed into 3-deoxy-D-arabino-heptulosonate-7-phosphate through a phospho-2-dehydro-3-deoxyheptonate aldolase. This is followed by a 3-dehydroquinate synthase converting the 3-deoxy-D-arabino-heptulosonate-7-phosphate into a 3-dehydroquinate which in turn is conveted to 3-dehydroshikimate through a 3-dehydroquinate dehydratase. At this point 3-dehydroshikimate can be turned into Shikimic acid through 2 different reactions involving Quinate/shikimate dehydrogenase and shikimate dehydrogenase 2. Shikimic acid is phosphorylated by Shikimate kinase 2 into shikimate 3-phosphate. Shikimate 3- phophate and a phosphoenolpyruvic acid are then joined through a 3-phosphoshikimate 1-carboxyvinyltransferase to produce a 5-enoylpyruvyl-shikimate 3-phosphate while releasing a phosphate. This in turn produces our final product Chorismate through a chorismate synthase.

Cardiolipin (CL) is an important component of the inner mitochondrial membrane where it constitutes about 20% of the total lipid composition. It is essential for the optimal function of numerous enzymes that are involved in mitochondrial energy metabolism (Wikipedia). Cardiolipin biosynthesis occurs mainly in the mitochondria, but there also exists an alternative synthesis route for CDP-diacylglycerol that takes place in the endoplasmic reticulum. This second route may supplement this pathway. All membrane-localized enzymes are coloured dark green in the image. First, dihydroxyacetone phosphate (or glycerone phosphate) from glycolysis is used by the cytosolic enzyme glycerol-3-phosphate dehydrogenase [NAD(+)] to synthesize sn-glycerol 3-phosphate. Second, the mitochondrial outer membrane enzyme glycerol-3-phosphate acyltransferase esterifies an acyl-group to the sn-1 position of sn-glycerol 3-phosphate to form 1-acyl-sn-glycerol 3-phosphate (lysophosphatidic acid or LPA). Third, the enzyme 1-acyl-sn-glycerol-3-phosphate acyltransferase converts LPA into phosphatidic acid (PA or 1,2-diacyl-sn-glycerol 3-phosphate) by esterifying an acyl-group to the sn-2 position of the glycerol backbone. PA is then transferred to the inner mitochondrial membrane to continue cardiolipin synthesis. Fourth, magnesium-dependent phosphatidate cytidylyltransferase catalyzes the conversion of PA into CDP-diacylglycerol. Fifth, CDP-diacylglycerol--glycerol-3-phosphate 3-phosphatidyltransferase synthesizes phosphatidylglycerophosphate (PGP). Sixth, phosphatidylglycerophosphatase and protein-tyrosine phosphatase dephosphorylates PGP to form phosphatidylglycerol (PG). Last, cardiolipin synthase catalyzes the synthesis of cardiolipin by transferring a phosphatidyl group from a second CDP-diacylglycerol to PG. It requires a divalent metal cation cofactor.

Cardiolipin (CL) is an important component of the inner mitochondrial membrane where it constitutes about 20% of the total lipid composition. It is essential for the optimal function of numerous enzymes that are involved in mitochondrial energy metabolism (Wikipedia). Cardiolipin biosynthesis occurs mainly in the mitochondria, but there also exists an alternative synthesis route for CDP-diacylglycerol that takes place in the endoplasmic reticulum. This second route may supplement this pathway. All membrane-localized enzymes are coloured dark green in the image. First, dihydroxyacetone phosphate (or glycerone phosphate) from glycolysis is used by the cytosolic enzyme glycerol-3-phosphate dehydrogenase [NAD(+)] to synthesize sn-glycerol 3-phosphate. Second, the mitochondrial outer membrane enzyme glycerol-3-phosphate acyltransferase esterifies an acyl-group to the sn-1 position of sn-glycerol 3-phosphate to form 1-acyl-sn-glycerol 3-phosphate (lysophosphatidic acid or LPA). Third, the enzyme 1-acyl-sn-glycerol-3-phosphate acyltransferase converts LPA into phosphatidic acid (PA or 1,2-diacyl-sn-glycerol 3-phosphate) by esterifying an acyl-group to the sn-2 position of the glycerol backbone. PA is then transferred to the inner mitochondrial membrane to continue cardiolipin synthesis. Fourth, magnesium-dependent phosphatidate cytidylyltransferase catalyzes the conversion of PA into CDP-diacylglycerol. Fifth, CDP-diacylglycerol--glycerol-3-phosphate 3-phosphatidyltransferase synthesizes phosphatidylglycerophosphate (PGP). Sixth, phosphatidylglycerophosphatase and protein-tyrosine phosphatase dephosphorylates PGP to form phosphatidylglycerol (PG). Last, cardiolipin synthase catalyzes the synthesis of cardiolipin by transferring a phosphatidyl group from a second CDP-diacylglycerol to PG. It requires a divalent metal cation cofactor.

Cardiolipin (CL) is an important component of the inner mitochondrial membrane where it constitutes about 20% of the total lipid composition. It is essential for the optimal function of numerous enzymes that are involved in mitochondrial energy metabolism (Wikipedia). Cardiolipin biosynthesis occurs mainly in the mitochondria, but there also exists an alternative synthesis route for CDP-diacylglycerol that takes place in the endoplasmic reticulum. This second route may supplement this pathway. All membrane-localized enzymes are coloured dark green in the image. First, dihydroxyacetone phosphate (or glycerone phosphate) from glycolysis is used by the cytosolic enzyme glycerol-3-phosphate dehydrogenase [NAD(+)] to synthesize sn-glycerol 3-phosphate. Second, the mitochondrial outer membrane enzyme glycerol-3-phosphate acyltransferase esterifies an acyl-group to the sn-1 position of sn-glycerol 3-phosphate to form 1-acyl-sn-glycerol 3-phosphate (lysophosphatidic acid or LPA). Third, the enzyme 1-acyl-sn-glycerol-3-phosphate acyltransferase converts LPA into phosphatidic acid (PA or 1,2-diacyl-sn-glycerol 3-phosphate) by esterifying an acyl-group to the sn-2 position of the glycerol backbone. PA is then transferred to the inner mitochondrial membrane to continue cardiolipin synthesis. Fourth, magnesium-dependent phosphatidate cytidylyltransferase catalyzes the conversion of PA into CDP-diacylglycerol. Fifth, CDP-diacylglycerol--glycerol-3-phosphate 3-phosphatidyltransferase synthesizes phosphatidylglycerophosphate (PGP). Sixth, phosphatidylglycerophosphatase and protein-tyrosine phosphatase dephosphorylates PGP to form phosphatidylglycerol (PG). Last, cardiolipin synthase catalyzes the synthesis of cardiolipin by transferring a phosphatidyl group from a second CDP-diacylglycerol to PG. It requires a divalent metal cation cofactor.

Nicotinamide adenine dinucleotide (NAD) can be biosynthesized from L-aspartic acid. This amino acid reacts with oxygen through an L-aspartate oxidase resulting in a hydrogen ion, hydrogen peroxide and an iminoaspartic acid. The latter compound interacts with dihydroxyacetone phosphate through a quinolinate synthase A, resulting in a phosphate, water, and a quinolic acid. Quinolic acid interacts with phosphoribosyl pyrophosphate and hydrogen ion through a quinolinate phosphoribosyltransferase resulting in pyrophosphate, carbon dioxide and nicotinate beta-D-ribonucleotide. The latter is adenylated through an ATP driven nicotinate-mononucleotide adenylyltransferase releasing a pyrophosphate and resulting in a nicotinic acid adenine dinucleotide. Nicotinic acid adenine dinucleotide is processed through an NAD synthetase, NH3-dependent in two different manners. In the first case, Nicotinic acid adenine dinucleotide interacts with ATP, L-glutamine and water through the enzyme and results in hydrogen ion, AMP, pyrophosphate, L-glutamic acid and NAD. In the second case, Nicotinic acid adenine dinucleotide interacts with ATP and ammonium through the enzyme resulting in a pyrophosphate, AMP, hydrogen ion and NAD. NAD then proceeds to regulate its own pathway by repressing L-aspartate oxidase. As a general rule, most prokaryotes utilize the aspartate de novo pathway, in which the nicotinate moiety of NAD is synthesized from aspartate , while in eukaryotes, the de novo pathway starts with tryptophan.