The genetic basis of myoadenylate deaminase deficiency is heterogeneous.

Abstract

Myoadenylate deaminase (MAD) is the muscle specific isoform of adenosine monophosphate deaminase (AMPD). AMPD (EC 3.5.4.6.) is an aminohydrolase that catalyzes the deamination of AMP to inosine monophosphate (IMP) with liberation of ammonia from position 6 of the adenine ring. As part of the purine nucleotide cycle,1,2 AMPD is involved in the regulation of the relative concentrations of intracellular purine nucleotides, the stabilization of the adenylate energy charge, the replenishment of citric acid cycle intermediates by the formation of fumarate, the deamination of amino acids (aspartate) and the regulation of the activity of the glycolytic enzymes phosphofructokinase and phosphorylase b.3–5 The fact that AMPD is an ubiquitous enzyme found in eukaryotes and in all tissues of vertebrates6–8 underlines the important role of this enzyme in energy metabolism. In man there are at least three isozymes. The isozyme with the highest activity is myoadenylate deaminase found in skeletal muscle.6,9