A colorimetric assay for serial determination of adenosine deaminase activity in small lymphocyte populations

We describe here an easy, sensitive and quantitative assay for the determination of adenosine deaminase activity in small populations of lymphoid cells. Determinations of enzyme activity and protein concentration are based on colorimetric reactions. All steps are directly performed in 96-well flat-bottom microtiter plates: growth of lymphoid cells (1-2 X 10(5) cells needed), detergent-mediated lysis, incubations for enzymatic assay, and reading of colorimetric reactions with an automatic multiscan spectrophotometer. Thus, screening of several hundred independent cell cultures is easily done within a day. Applications to the detection of rare adenosine deaminase variants from large cell populations and to routine medical assays are considered.