SUBUNIT COMPOSITION OF AMPD VARIES IN RESPONSE TO CHANGES IN AMPD1 AND AMPD3 GENE-EXPRESSION IN SKELETAL-MUSCLE

Adenosine monophosphate deaminase (AMPD), a central enzyme in energy m etabolism in skeletal muscle, is encoded by a multigene family in high er eukaryotes, Denervation was used as a stimulus to induce a change i n fiber type composition of rat gastrocnemius muscle and, consequently , gene expression. Specific antisera and nucleic acid probes were used to assess changes in expression of the AMPD 1 and AMPD3 genes. Total AMPD activity in denervated skeletal muscle increased by 34%. The comp osition of the AMPD tetrameric holoenzyme was altered in two ways: The percentage of AMPD holoenzyme molecules consisting of one or more AMP D3 subunits increased three-fold, and the percentage of AMPD 1 mRNA th at excludes exon 2-encoded sequences doubled. These results suggest th at expression of the AMPD1 and AMPD3 genes may be coordinated myocytes to effect production of an AMPD holoenzyme of varying subunit composi tion.