Cloning of human adenosine deaminase cDNA and expression in mouse cells

A previously isolated partial cDNA sequence encoding human adenosine deaminase (ADA) was used to probe a cDNA library prepared from human cultured cell mRNA. Clones containing a combined overlapping length of 1462 bp were isolated and sequenced. One of these was found to include the entire ADA coding region. An open reading frame consisting of 363 codons was identified, predicting a polypeptide of Mr 40762. A mammalian expression plasmid was constructed, positioning the ADA coding sequence to be under transcriptional control of the mouse metallothionein promoter. Transfection of cultured mouse L-cells with this plasmid resulted in the acute expression of human ADA enzymatic activity, as assayed by isoelectric focusing.