Molecular Basis for Human Erythrocyte AMP deaminase deficiency.

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In humans, there are three fundamental isoforms of AMP deaminase, and the gene AMPD-1 encodes muscle-type isozyme, AMPD-2 encodes liver-type, and AMPD-3 encodes erythrocyte AMP deaminase. The human erythrocyte AMP deaminase deficiency first identified by us. In this study, we performed the molecular analysis of gene mutation responsible for the deficiency.1) A major point mutation of C to T (R573C) on the AMPD-3 has been identified by molecular analysis of the genetic materials from the enzyme deficient individuals.2) Screening of 2,600 Japanese blood samples suggested that the human erythrocyte AMP deaminase deficiency in Japanese is associated with 75 % of the major mutation (R573C) and 25 % of other mutations. Nine heterogeneous new mutations (600delT,N310K,A320V,M324T,R331C,R402C,Q433X,W445R,and P585L) were identified from the analyzes of cDNA and genomic DNA.3) The results from expression studies using E.coli confirmed that the major mutation (R573C) led to a catalytically inactive but stable peptide.4) The structure of the AMPD-3 has been examined by the PCR technique and direct sequencing. The nucleotide sequences around all exon/intron junctions have been elucidated. The gene locus, spanning about 50 kb, was amplified to six separate DNA fragments by the technique of LA-PCR.