Characteristics of an aminohydrolase distinct from adenosine deaminase in cultured human lymphoblasts.

An inherited deficiency of adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) is associated with an autosomal recessive form of severe combined immunodeficiency disease. Affected patients exhibit markedly reduced or absent adenosine deaminating activity in various tissues. In this study we have demonstrated the presence of a low level aminohydrolase activity in 11 different normal and adenosine deaminase-deficient lymphoblast cell lines which is apparently distinct from normal adenosine deaminase. Based on enzymatic, physical and immunoreactive properties, this lymphoblast aminohydrolase does not appear to be related to adenosine deaminase and is most likely coded for by a different gene locus. In future investigations designed to characterize mutant forms of adenosine deaminase, it will be important to distinguish this lymphoblast aminohydrolase activity from putative products of the adenosine deaminase gene locus.