Browsing Pathways

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.

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.

NADH dehydrogenase and nitrate reductase can form the anaerobic respiratory chain that can be used for transferring electrons from NADH to nitrate with proton-motive force across cytoplasmic membrane. In E. coli K-12, NDH-I and NDH-II is the two energy conserving NADH dehydrogenases that do not contribute to proton gradient; but both of the enzymes are involved in anaerobic nitrate respiration. NDH-I might be acted as proton pump for translocating 4H+ per NADH oxidised (2e-). In E. coli K-12, there are also two energy conserving (H+/e- = 1) nitrate reductases (nitrate reductase A (NRA) and nitrate reductase Z (NRZ)). Nitrate reductase A can express under the condition of high levels of nitrate in environment; while the expression of nitrate reductase Z doesn't depend on nitrate levels or anaerobiosis. Nitrate and hydrogen atom will be catalyzed to form nitrite and water during nitrate reduction.

E. coli K-12 can utilize six existing hexitols as source of carbon and energy. Hexitols can enter bacterial cell by specific phosphotransferase system, which is consisted of mannose permease IID component, mannose permease IIC component and PTS system mannose-specific EIIAB component. Sorbitol-6-phosphate will be converted to fructose 6-phosphate by sorbitol-6-phosphate dehydrogenase with cofactor NAD. Sorbitol-6-phosphate will be transformed into β-D-Fructose 6-phosphate spontaneously, which the later product will undergo glycolysis I.

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 K-12 can utilize six existing hexitols as source of carbon and energy. Hexitols can enter bacterial cell by specific phosphotransferase system, which is consisted of mannose permease IID component, mannose permease IIC component and PTS system mannose-specific EIIAB component. Sorbitol-6-phosphate will be converted to fructose 6-phosphate by sorbitol-6-phosphate dehydrogenase with cofactor NAD. Sorbitol-6-phosphate will be transformed into β-D-Fructose 6-phosphate spontaneously, which the later product will undergo glycolysis I.

E. coli K-12 can utilize six existing hexitols as source of carbon and energy. Hexitols can enter bacterial cell by specific phosphotransferase system, which is consisted of mannose permease IID component, mannose permease IIC component and PTS system mannose-specific EIIAB component. Sorbitol-6-phosphate will be converted to fructose 6-phosphate by sorbitol-6-phosphate dehydrogenase with cofactor NAD. Sorbitol-6-phosphate will be transformed into β-D-Fructose 6-phosphate spontaneously, which the later product will undergo glycolysis I.