Stabilization of phospho-intermediates of rat liver plasma membrane alkaline phosphatase by uncompetitive inhibition. Relation with phosphate uptake into hepatocytes.
Rat liver plasma membrane alkaline phosphatase (ALP) phospho-intermediates, which have molecular masses of 151 and 135 kDa bands, were labelled at physiological pH with either (gamma-32P) ATP or 32Pi. This labeling was stabilized by a potent enzyme inhibitor, bromolevamisole (BL), and not by bromodexamisole (BD). BL augmented the rate and extent of autophosphorylation and slowed down the rate of autodephosphorylation of ALP. The phospho-intermediates labeling presented nearly the same kinetic behaviour with either (gamma-32P) ATP or 32Pi. In the presence of BL a marked decrease of the phosphorylation state of many proteins was observed in hepatocytes. BL also produced a decrease of the 32Pi uptake into hepatocytes and a decrease of the specific radioactivity of cellular ATP. BD had nearly the same effect as BL on protein phosphorylation and 32Pi uptake. These results argued against a direct involvement of ALP in Pi transport across hepatocyte plasma membrane.
Sarrouilhe
D
D
Groupe de Recherche et d'Etude d' Analogues de Médicaments, Faculté de Médecine et de Pharmacie, Poitiers, France.
Métayé
T
T
Rivet
G
G
Lalégerie
P
P
Baudry
M
M
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000469:Alkaline Phosphatase / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D007978:Levamisole / Q000031:analogs & derivatives / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D010710:Phosphates / Q000378:metabolism*; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D051381:Rats; D017208:Rats, Wistar; D013773:Tetramisole / Q000031:analogs & derivatives / Q000494:pharmacology; D013997:Time Factors
D010710:Phosphates; D010750:Phosphoproteins; D010761:Phosphorus Radioisotopes; D007978:Levamisole; C006226:4-bromotetramisole; D000255:Adenosine Triphosphate; D013773:Tetramisole; D000469:Alkaline Phosphatase