PHOSPHORYLATION OF ADENOSINE IN RENAL BRUSH-BORDER MEMBRANE-VESICLES BY AN EXCHANGE-REACTION CATALYZED BY ADENOSINE KINASE

Uptake of [H-3]adenosine in brush-border membrane (BBM) vesicles from either rat or pig kidney leads to an accumulation of intravesicular [H -3]AMP. The lack of significant levels of ATP and the presence of AMP in BBM indicated that a phosphotransfer between [H-3]adenosine and AMP occurs. The phosphotransfer activity is inhibited by iodotubercidin, which suggests that it is performed by adenosine kinase acting in an A TP-independent manner. The existence of a similar phosphotransferase a ctivity was demonstrated in membrane-free extracts from pig kidney. Fr om the compounds tested it was shown that a variety of mononucleotides could act as phosphate donors. The results suggest that phosphotransf er reactions may be physiologically relevant in kidney.