Portal de Periódicos da CAPES

Mode of orthophosphate uptake and ATP labeling by mammalian cells

1976; Elsevier BV; Volume: 443; Issue: 3 Linguagem: Inglês

10.1016/0005-2787(76)90513-x

1879-3002

Walter G. Niehaus, Roy H. Hammerstedt,

Mitochondrial Function and Pathology

Incubation of HeLa cells with [32P]orthophosphate results in more rapid labeling of the γ-phosphorus of ATP than of the intracellular pool of orthophosphate. The specific radioactivity of ATP equals that of extracellular orthophosphate after 2 h of incubation. A similar pattern of labeling is seen with human erythrocytes when incubated at physiological concentrations of orthophosphate (2 mM) and pH 7.4–7.8. At lower pH, 6.8–7.2, the rate of orthophosphate uptake increases and exceeds the rate of labeling of ATP. These data are explained by the existence of a primary system for ATP uptake which involves the mediation of membrane-bound glyceraldehyde-3-phosphate dehydrogenase. Phosphate first enters the cell as 1,3-diphospholyceric acid, is then transferred to ATP, and then enters the intracellular orthophosphate pool. At lower pH monovalent orthophosphate also enters the erythrocyte by a process not involving glyceraldehyde-3-phosphate dehydrogenase.