Phosphorylation, efficiency

Ethanol accumulated in maturing citrus fruit as the end product of pyruvate decarboxylation. Conditions that promote this reaction include low and high CC, and ethylene levels. Maturation increased the levels of PDC and ADH and increased the NADH to NAD ratio. The higher redox ratio could slow the PDH reaction which competes with PDC for pyruvate. Development of the alternative oxidase activity when ethanol began to accumulate suggests that membrane function was modified which affected rates of various metabolic pathways. The lower phosphorylation efficiency of the alternative oxidase compared to the cytochrome pathway (22) could affect numerous metabolic activities including decarboxylation of pyruvate. Also, membrane transport of pyruvate and cofactors could be altered in mitochondria containing fewer phosphorylation sites (26). 

Presently we are proceeding to use the synthetic peptides for cross linking studies, in order to identify protein kinases present, and as affinity ligands in protein kinase purification. The use of peptides that are somewhat longer (20-40 residues) than the short peptides used in this study should allow an assessment of the contribution made by secondary structure to substrate phosphorylation efficiency. 

Nada et al. studied the influence of the corn cobs treatment, before phosphorylation, with different concentrations of the NaOH solution upon the phosphorylation efficiency and upon the metal ions adsorption. They demonstrated that the use of a 7.5% NaOH solution lead to the highest level of phosphate groups which were incorporated into the treated corn cobs. The modified cellulose was washed several times with distilled water (and maybe acetone, or an alcohol), dried, and then could be used in further experiments. In the phosphorylation process the phosphoric group should be introduced at the primary carbon with hydroxyl groups and the phosphorylation is complete when all the C-OH groups are substituted. ... 

Gnaiger E, Mendez G, Hand SC. High phosphorylation efficiency and depression of uncoupled respiration in mitochondria under hypoxia. Proc Natl Acad Sci USA 2000 97 11080-11085. 

To gain further insight into the age-related adaptation of skeletal muscle to a more aerobic-oxidative metabolism, studying mitochondrial bioenergetic parameters and mitochondrial oxidative phosphorylation efficiency is of crucial importance. 

Whereas phosphorylation efficiency dropped during ADP limitation under normoxia, P 0 ratios were conservatively five-fold higher under severe hypoxia, when oxygen consumption was limited by oxygen supply. A reduction in proton leakage across the inner membrane under hypoxia could potentially explain the observation, which would decrease state 4 respiration. The proton permeability of the inner mitochondrial membrane is dependent on the physical properties of... 

Our previous analysis (McCarty, Portis, 1976 Davenport, 1983) of ATP synthesis and hydrolysis in relation to proton fluxes provided evidence that the common link between electron transport and ATP synthesis in the steady state is a proton activity gradient (ApH). From this analysis, we also derived a maximal phosphorylation efficiency (P/c2)max close to 4/3. The (P/c2)niax equivalent to 2 (H+/e ) / (H+/ATP), where H+/e is the ratio of protons appearing in the thylakoid interior to electrons transferred and H+/ATP is the ratio of protons translocated to ATP synthesized. Thus, if the (H+/e ) is 2, (H" /ATP) is three. (H+/ATP) ratios of three have been obtained by other methods (Avron, 1978 Hand-garter, Good, 1982). 

Two and twelve moles of ATP are produced, respectively, per mole of glucose consumed in the glycolytic pathway and each turn of the Krebs (citrate) cycle. In fat metaboHsm, many high energy bonds are produced per mole of fatty ester oxidized. Eor example, 129 high energy phosphate bonds are produced per mole of palmitate. Oxidative phosphorylation has a remarkable 75% efficiency. Three moles of ATP are utilized per transfer of two electrons, compared to the theoretical four. The process occurs via a series of reactions involving flavoproteins, quinones such as coenzyme Q, and cytochromes. 

An alternative method involves reaction of an a-acylaminoketone (12) with a primary amine and subsequent ring closure of the resultant Schiff s base (13) with phosphoryl chloride. This enables the introduction of a 1-substituent as in (14) to be carried out efficiently, and if the amine were replaced with a monosubstituted hydrazine, the imidazole derivative (IS) resulted (78LA1916). 

Increase. Increased efficiency of oxidative phosphorylation increases the P/O quotient See E - 3.3. 

The natural acceptor aldehyde can be considerably varied among phosphorylated as well as unphosphorylated hydroxyaldehydes, which are both converted at comparable rates (Table 5)13-44 47. Although the catalytic reaction creates only a single stereocenter, the enzymes from yeast or spinach efficiently distinguish between adjacent configurations with preference for (3SAR)-i>yn isomeric ketose products44 47, which nicely parallel those derived from FruA reactions (Section 1.3.4.6.1). 

PSI-6130, upon phosphorylation to its 5 -triphosphate, is incorporated (as PSl-6130-MP) as a nonobligate chain terminator (Murakami et al. 2008) into RNA catalyzed by purified RNA-dependent RNA polymerase (NS5B). PSl-6130 is metabolized intracellularly to the 5 -triphosphate of p-D-2 -deoxy-2 -fluoro-2 -C-methyluridine (PSI-6206) (Ma et al. 2007), but, as compared to the 5 -triphosphate of PSI-6130, the 5 -triphosphate of PSI-6206 is less efficient an inhibitor of HCV RNA-dependent RNA polymerase than PSI-6130 5 -triphosphate (Murakami et al. 2007). 

The method has then been efficiently used to remove selectively the exocycHc methylsulfanyl group from phosphorylated thiopyranyl derivatives 85 resulting from hetero Diels-Alder reaction of a phosphono-dithioformate or dithioacetate (see Sects. 2.1.2 and 2.2.3). FimctionaHzed thiopyrans 86 [17,18,27a] are thus obtained (Scheme 25). Owing to this selective desulfanylation, phospho-nodithioesters can be used as heterodienophiles in place of the corresponding phosphonothioaldehyde, not described so far and probably very unstable. 

Chiral phosphoryl and sulfinyl groups are known as efficient auxiliaries in asymmetric synthesis. As reported below, their asymmetric induction in the a-posi-tion has been used to prepare chiral non-racemic organophosphorus compounds a-substituted by a sulfur function. Such compounds can also be obtained from their a-hydroxy analogues by OH-4 SR stereoselective transformation. 

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