Browsing Pathways

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.

The acetate biosynthesis starts with acetyl-CoA reacting with phosphate through a phosphate acetyltransferase resulting in the release of a coenzyme A and an acetyl phosphate. The latter compound in turn reacts with ADP through an acetate kinase resulting in the release of an ATP and an acetate. The acetate reacts with ATP and coenzyme A through an acetyl-CoA synthase resulting in the release of a diphosphate, an AMP and an acetyl-CoA. Acetyl-CoA can be biosynthesized by acetoacetate reacting with an acetyl-CoA through an acetoacetyl-CoA transferase resulting in the release of an acetate and an acetoacetyl-CoA. The acetoacetyl-CoA reacts with an acetyl-CoA acetyltransferase resulting in the release of an coenzyme A and 2 acetyl-CoA

The cyanate degradation pathway begins with the transportation of cyanate into the cytosol through a cynX transporter. Once inside the cytosol cyanate reacts with hydrogen carbonate and a hydrogen ion through a cyanase resulting in the release of carbon dioxide and carbamate. Carbamate reacts spontaneously with hydrogen resulting in the release of ammonium and carbon dioxide. Carbon dioxide reacts with water through carbonic anhydrase resulting in the release of hydrogen ion and hydrogen carbonate.

The cyanate degradation pathway begins with the transportation of cyanate into the cytosol through a cynX transporter. Once inside the cytosol cyanate reacts with hydrogen carbonate and a hydrogen ion through a cyanase resulting in the release of carbon dioxide and carbamate. Carbamate reacts spontaneously with hydrogen resulting in the release of ammonium and carbon dioxide. Carbon dioxide reacts with water through carbonic anhydrase resulting in the release of hydrogen ion and hydrogen carbonate.

The cyanate degradation pathway begins with the transportation of cyanate into the cytosol through a cynX transporter. Once inside the cytosol cyanate reacts with hydrogen carbonate and a hydrogen ion through a cyanase resulting in the release of carbon dioxide and carbamate. Carbamate reacts spontaneously with hydrogen resulting in the release of ammonium and carbon dioxide. Carbon dioxide reacts with water through carbonic anhydrase resulting in the release of hydrogen ion and hydrogen carbonate.

The cyanate degradation pathway begins with the transportation of cyanate into the cytosol through a cynX transporter. Once inside the cytosol cyanate reacts with hydrogen carbonate and a hydrogen ion through a cyanase resulting in the release of carbon dioxide and carbamate. Carbamate reacts spontaneously with hydrogen resulting in the release of ammonium and carbon dioxide. Carbon dioxide reacts with water through carbonic anhydrase resulting in the release of hydrogen ion and hydrogen carbonate.

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.

Wild-Type E.coli K-12 can not directly use D-arabinose as a sole source of carbon and energy; hence, E.coli uses the enzymes of the fucose degradation pathway to degrade D-arabinose for further utilization. D-arabinose can be metabolized to form dihydroxy-acetone phosphate for entering the central metabolism. Glycolaldehyde can be further catalyzed to form glycolic acid by lactaldehyde dehydrogenase.

Wild-Type E.coli K-12 can not directly use D-arabinose as a sole source of carbon and energy; hence, E.coli uses the enzymes of the fucose degradation pathway to degrade D-arabinose for further utilization. D-arabinose can be metabolized to form dihydroxy-acetone phosphate for entering the central metabolism. Glycolaldehyde can be further catalyzed to form glycolic acid by lactaldehyde dehydrogenase.