Adenosine deaminase is a purine catabolic enzyme ubiquitous in mammalian tissue which catalyzes deamination of both adenosine and 2'-deoxyadenosine to inosine and 2'-deoxyinosine respectively. Adenosine deaminase is useful in various molecular biology assays, such as glycerol release assays. Adenosine deaminase is a potential target for treatments of combined immunodeficiency disease.