Adenosine deaminase that may contribute to the degradation of extracellular adenosine, a signaling molecule that controls a variety of cellular responses. Requires elevated adenosine levels for optimal enzyme activity. Binds to cell surfaces via proteoglycans and may play a role in the regulation of cell proliferation and differentiation, independently of its enzyme activity. {ECO:0000269|PubMed:20147294, ECO:0000269|PubMed:20453107}. This is the function of ENSG00000093072 (ADA2, adenosine deaminase 2).