Cytoplasmic phosphate

Both 27Al and 31P NMR have been used to study the uptake of Al3+ by cell suspensions of the alga Chlorella saccaraphila (Folsom et al., 1986). The results were interpreted as indicating Al complexation with cytoplasmic phosphates, and inhibition of glucose metabolism. 

The role of PolyP as a buffer was demonstrated in N. crassa under osmotic stress where the hypoosmic shock produced a rapid hydrolysis of the PolyP with an increase in the concentration of cytoplasmic phosphate (Yang et al, 1993). 

Figure 7.11 Relationship between NADH redox state and predicted mitochondrial membrane potential at different levels of cytoplasmic ADR The cytoplasmic ADP concentration is fixed at the values indicated and the cytoplasmic ATP concentration is computed [ATPC] = 8.2 mM - [ADPC] cytoplasmic phosphate [PIC] is...

Figure 7.12 Predicted relationship between the rate of delivery of ATP out of the mitochondrion and the cytoplasmic ADP concentration. For these model predictions, the cytoplasmic ATP concentration is computed as a function of [ADPC] as described in the legend to Figure 7.11 cytoplasmic phosphate [PIC] is clamped at 1 mM.

Figure 4 Representative NMR spectra (161.93 MHz) of sucrose-supplied and sucrose-deprived (120 h) sycamore cells. Cells harvested from the culture medium were rinsed three times by successive resuspensions in fresh culture medium devoid of sucrose and incubated at zero time (20 mg wet weight / ml) into flasks containing sucrose-free culture medium. Cells (normal cells and 120-h sucrose starved cells (9 g) were harvested for in vivo examination. The spectra recorded at 20 C with a 50° pulse angle and a 0.6-s repetition time were the result of 6000 transients (1 h). Perfusion medium A, standard culture medium B, culture medium devoid of sucrose since 120 h. Peak assigments Glc-6-P, glucose-6-P Fru-6-P, fhictose-6-P Cyt-pi, cytoplasmic phosphate (at pH 7.5) vac-Pi, vacuolar phosphate (at pH 5.7) NTP, nucleotides triphosphate UDPG, uridine-5 -diphosphate-a-D-glucose...

FIGURE 8.18 Dolichol phosphate is an initiation point for the synthesis of carbohydrate polymers in animals. The analogous alcohol in bacterial systems, undecaprenol, also known as bactoprenol, consists of 11 isoprene units. Undecaprenyl phosphate delivers sugars from the cytoplasm for the synthesis of cell wall components such as peptidoglycans, lipopolysaccharides, and glycoproteins. Polyprenyl compounds also serve as the side chains of vitamin K, the ubiquinones, plastoquinones, and tocopherols (such as vitamin E). 

FIGURE 10.10 The reaction of tridated sodium borohydride with the aspartyl phosphate at the active site of Na, K -ATPase. Acid hydrolysis of the enzyme following phosphorylation and sodium borohydride treatment yields a tripeptide containing serine, homoserine (derived from the aspartyl-phosphate), and lysine as shown. The site of phosphorylation is Asp" in the large cytoplasmic domain of the ATPase. 

In the glycerophosphate shuttle, two different glycerophosphate dehydrogenases, one in the cytoplasm and one on the outer face of the mitochondrial inner membrane, work together to carry electrons into the mitochondrial matrix (Figure 21.32). NADH produced in the cytosol transfers its electrons to dihydroxyaeetone phosphate, thus reducing it to glyeerol-3-phosphate. This metabolite is reoxidized by the FAD -dependent mitochondrial membrane enzyme to... 

The mannose 6-phosphate receptor is the cargo/coat-receptor for trans-Golgi network (TGN)-derived cla-thrin vesicles. The receptor recognizes the mannose 6-phosphate tag of lysosomal hydrolases on the luminal side and the adaptor-1 complex of clathrin on the cytoplasmic face. 

Furthermore, if the antibiotic passes membranes through a specific port of entry, its mutational loss leads to resistance. The lack of the outer membrane protein OprD in P. aeruginosa causes resistance to the (3-lactam antibiotic imipenem. Fosfomycin passes the cytoplasmic membrane via an L-a-glycerol phosphate permease. This transport system is not essential for bacterial growth and therefore mutants with a reduced expression are frequently selected under therapy. 

Figure 48-12. Schematic illustration of some aspects of the role of the osteoclast in bone resorption. Lysosomal enzymes and hydrogen ions are released into the confined microenvironment created by the attachment between bone matrix and the peripheral clear zone of the osteoclast. The acidification of this confined space facilitates the dissolution of calcium phosphate from bone and is the optimal pH for the activity of lysosomal hydrolases. Bone matrix is thus removed, and the products of bone resorption are taken up into the cytoplasm of the osteoclast, probably digested further, and transferred into capillaries. The chemical equation shown in the figure refers to the action of carbonic anhydrase II, described in the text. (Reproduced, with permission, from Jun-queira LC, Carneiro J BasicHistology. Text Atlas, 10th ed. McGraw-Hill, 2003.)...

The calcium phosphate method was first used in 1973 to introduce adenovirus DNA into mammalian cells [3]. DNA-Calcium-phosphate complexes are formed by mixing DNA in a phosphate buffer with calcium chloride. These complexes adhere to the cell membrane and enter the cytoplasm by endocytosis. Disadvantages of DEAE-dextran and calcium phosphate transfection are a certain level of cytotoxicity, a complicated transfection procedure, and the fact that not all cell types can be transfected using these methods. 

Fig. 8.1 Biosynthesis of peptidoglycan. The large circles represent A -acetylglucosamine orN-acetylmuramic acid to the latter is linked initially a pentapeptide chain comprising L-alanine, D-glutamic acid and meso-diaminopiraelic acid (small circles) terminating in two D-alanine residues (small, darker circles). The lipid molecule is undecaprenyl phosphate. In the initial (cytoplasm) stage where inhibition by the antibiotic D-cycloserine is shown, two molecules of Dalanine (small circles) are converted by an isomerase to the D-forms (small, darker circles), alter which a ligase joins the two D-alanines together to produce a D-alanyl-D-alanine dipeptide.

By contrast, the cytoplasmic decarboxylation of dopa to dopamine by the enzyme dopa decarboxylase is about 100 times more rapid (Am 4x 10 " M) than its synthesis and indeed it is difficult to detect endogenous dopa in the CNS. This enzyme, which requires pyridoxal phosphate (vitamin B6) as co-factor, can decarboxylate other amino acids (e.g. tryptophan and tyrosine) and in view of its low substrate specificity is known as a general L-aromatic amino-acid decarboxylase. 

In plant plastids, GGPP is formed from products of glycolysis and is eight enzymatic steps away from central glucose metabolism. The MEP pathway (reviewed in recent literature - ) operates in plastids in plants and is a preferred source (non-mevalonate) of phosphate-activated prenyl units (IPPs) for plastid iso-prenoid accumulation, such as the phytol tail of chlorophyll, the backbones of carotenoids, and the cores of monoterpenes such as menthol, hnalool, and iridoids, diterpenes such as taxadiene, and the side chains of bioactive prenylated terpenophe-nolics such as humulone, lupulone, and xanthohumol. The mevalonic pathway to IPP that operates in the cytoplasm is the source of the carbon chains in isoprenes such as the polyisoprene, rubber, and the sesquiterpenes such as caryophyllene. 

A well-known example of active transport is the sodium-potassium pump that maintains the imbalance of Na and ions across cytoplasmic membranes. Flere, the movement of ions is coupled to the hydrolysis of ATP to ADP and phosphate by the ATPase enzyme, liberating three Na+ out of the cell and pumping in two K [21-23]. Bacteria, mitochondria, and chloroplasts have a similar ion-driven uptake mechanism, but it works in reverse. Instead of ATP hydrolysis driving ion transport, H gradients across the membranes generate the synthesis of ATP from ADP and phosphate [24-27]. 

Tricresyl phosphate (a complex mixture containing tri-o, Xn-m-, and tri-para-cresyl phosphate that is used in certain hydraulic fluids) and TOCP are demonstrated testicular toxicants in rodents (Carlton et al. 1987 Somkuti et al. 1987a, 1987b). Tricresyl phosphate also has been shown to impair in vivo fertility in rats and mice (Carlton et al. 1987 Chapin et al. 1988a). In addition, tricresyl phosphate-treated female rats displayed vacuolar cytoplasmic alteration of ovarian interstitial cells (Carlton et al. 1987 NTP 1994). Reproductive effects have also been seen after oral exposure to butylated triphenyl phosphate (Latendresse et al. 1994b). 

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