Characterization of Adenosine Deaminating Activity in Normal and Adenosine Deaminase Deficient Human Tissue
The differing properties of residual enzyme activity converting adenosine to inosine in tissue of individuals with adenosine deaminase deficiency and severe combined immunodeficiency (1–5) reflect in part the limited amount of enzyme activity in these tissues and the molecular heterogeneity of adenosine deaminase in normal tissue. Human adenosine deaminase exists either as a particulate species or as one of two soluble interconvertible molecular forms designated the small and large forms (6). The large form of adenosine deaminase (Mr 280,000) is composed of two molecules of the small form (Mr 38,000) and one molecule of complexing protein (Mr 200,000) (6,7). In addition to these forms, analysis of normal tissue has revealed a low level of intermediate (Mr 110,000) activity (6) which in splenic tissue of an individual with adenosine deaminase deficiency and severe combined immunodeficiency was the exclusive form of adenosine deaminating activity (1). Subsequently Schrader et al (4) and Daddona and Kelley (5) have demonstrated with either splenic tissue or B lymphoblast derived from adenosine deaminase normal or deficient individuals, the presence of an aminohydrolase which differs from normal adenosine deaminase in its Km for adenosine, pH optimum, insensitivity to the potent adenosine deaminase inhibitor erythro-9-(2 hydroxy-3-nonyl)-adenine (EHNA) and its immunoreactivity with antibody to human adenosine deaminase. In this communication we report our findings on this distinct aminohydrolase in normal and adenosine deaminase deficient tissue.
KeywordsEnzyme Replacement Therapy Adenosine Deaminase Residual Enzyme Activity Severe Combine Immunodeficiency Splenic Tissue
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- 2.S.H. Chen, C.R. Scott and K.R. Swedberg. Heterogeneity for adenosine deaminase deficiency: Expression of the enzyme in cultured skin fibroblasts and amniotic fluid cells. Am. J. Hum. Genetic 27: 46 (1975).Google Scholar