Novel missense mutation found in a Japanese patient with myeloperoxidase deficiency.

Myeloperoxidase (MPO; EC 1.11.1.7) plays an important role in the host defense mechanism against microbial diseases. The neutrophil disorder characterized by the lack of MPO activity, is speculated to be associated with a decreased level of immunity. A Japanese patient was identified with complete MPO deficiency through automated hematography. Neutrophil function analysis revealed that MPO activity was significantly diminished with slightly elevated superoxide production. Mutational analysis of the patient revealed a glycine to serine substitution (G501S) in the exon 9 region. This mutation was not detected in the 96 healthy controls analyzed. The amino acid substitution found may be responsible for the failure of mature MPO production in the patient. This is the first case of MPO deficiency of G501S missense mutation identified in a Japanese patient.