Esterification of Adenosine Monophosphate Coupled with the Respiration of Heavy Beef Heart Mitochondria

Abstract

1. At the point of re-establishment of controlled respiration which was released by the addition of AMP, a significant amount of modified AMP, “AMP”, was found in the mitochondrial suspension.
2. Distribution of ¹⁴C-nucleotides and esterified ³²P in and outside of mitochondria proved that there was negligible accumulation of nucleotides by the mitochondria during oxidative phosphorylation.
3. Studies using 5'-adenylate deaminase showed that the conversion of AMP to “AMP” was a respiration-dependent process. The conversion proceeded in the absence of added phosphate, even though its rate was slow.
4. “AMP” was provisionally identified to be acyl-adenylate on thin layer chromatography by comparison of its Rf value with that of synthetic reference compounds other than both 5'-AMP and 3', 5'-cyclic AMP.
5. Parallel to the accumulation of “AMP” during state 3 respiration, there was accumulation of hydroxamate-reacting material. It was concluded that “AMP” might be a high energy ester derivative of AMP, possibly containing a substrate derived material.
6. The nature of “AMP” was discussed in relation with the transfer of high energy bonds across the mitochondrial membrane.