Cell Organic Phosphates with

The Mechanism of Interaction of Red Cell Organic Phosphates with Hemoglobin... 

Benesch, R.E.,and Benesch, R., 1974, The mechanism of interaction of red cell organic phosphates with hemoglobin, Adv. Protein Chem., 28 211. 

Phosphorus is found in every cell of the body, but most of it (about 80% of the total) is combined with calcium as Ca3(P04)2 in the bones and teeth (Harper 1969 Tietz 1970). Phosphorus is present in cells mainly as organic phosphate, with a small amount in serum as inorganic phosphate (Tietz 1970). Phosphorus is involved in the intermediary metabolism of carbohydrates (Tietz 1970). About 10% is found in combination with proteins, phospholipids, and carbohydrates and in other compounds in the blood and muscle (Harper 1969). The remaining phosphorus is widely distributed in various chemical compounds such as nucleic acids, nucleotides, and adenosine triphosphate (ATP) (Tietz 1970). 

APase in onion roots. Enzyme activity was mainly extracellular with the heaviest concentration in corner spaces between the epidermal and hypo-dermal layers. He suggested the possibility of a subcutaneous pore through which the enzyme could be released to the root surface. Bieleski and co-workers (Reid Bieleski, 1970 Bieleski Johnson, 1972) studied the psi induction and location of APase in duckweed (Spirodela oligorrhiza). APase in control plants was located primarily in and around the vascular strands. In P-deficient plants psi-APase activity was 10-20 times the control value. Enzyme activity was primarily located in the epidermis of the root and undersurface of the frond, the tissue locations most likely to provide access to phosphate esters in the medium. These workers further demonstrated that hydrolysis of organic phosphates occurred in the external medium and/or the apoplast followed by Pi uptake into the cell. 

Increased intake and a shift of phosphate from the tissues into the ECF are also causes of hyperphosphatemia. Excessive oral, rectal, or intravenous phosphate administration for the treatment of phosphate depletion is a common cause of hyperphosphatemia. Release of phosphate because of cell breakdown in cases of rhabdomyolysis, intravascular hemolysis, or chemotherapy of certain malignancies may cause hyperphosphatemia. Hyperphosphatemia may also be associated with acidosis, a consequence of the hydrolysis of intracellular organic phosphate-containing compounds, with the release of phosphate into the plasma. 

---