Acid maltase levels in muscle in heterozygous acid maltase deficiency and in non-weak and neuromuscular disease controls.

Acid maltase (AM) deficiency carriers can be detected by muscle enzyme assay. The assay indicates that, just as in infantile and childhood cases, adult cases of the disease are transmitted by autosomal recessive inheritance. With the maltose hydrolysis assay, in some neuromuscular diseases, muscle AM activity can be as low as in heterozygous AM deficiency. A relatively low muscle AM activity in myxoedema myopathy is confirmed. In human muscle, the K(m) of the enzyme for maltose hydrolysis is 7·2 to 9 × 10(-3)M. A modification of the enzyme assay based on this fact is recommended.