Evidence against direct transfer of the adenine nucleotides by the heart mitochondrial creatine kinase-adenine nucleotide translocase complex

Adenine nucleotide translocase inhibitors, atractyloside and carboxyatractyloside, added to respiration inhibited rat heart mitochondria had no significant effects on the apparent Km's for ATP and ADP and Vmax's of the creatine kinase reaction. The results suggest that there is no sequential, mandatory, direct transfer of the nucleotides between the translocase and the creatine kinase active site. The reaction was run in both the forward and reverse directions in media containing either 0.25 M sucrose or 0.13 M KCl. The apparent Km's, however, were found to be 2–3 times higher in the KCl medium than in sucrose, suggesting the use of the more physiological medium for meaningful kinetic studies.