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. adenosine + H(+) + H2O = inosine + NH4(+) Binds 1 zinc ion per subunit. Optimum pH is 6.6. Homodimer. Interacts with adenosine receptors. Binds heparin. Detected in blood plasma (at protein level). Widely expressed, with most abundant expression in human adult heart, lung, lymphoblasts, and placenta as well as fetal lung, liver, and kidney. In embryo, expressed in the outflow tract and atrium of the developing heart, the VII/VIII cranial nerve ganglion, and the notochord. The PRB domain is involved in receptor binding, and may be responsible for the cytokine-like growth factor activity due to it's sharing of several structural properties with chemokines. High-affinity binding to heparin/glycosaminoclycan (GAG) is mediated by a large, highly positively charged surface at the interface of dimer's subunits involving approximately residues 30-45, 389-396, and 422-428. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Candidate gene for the Cat Eye Syndrome (CES), a developmental disorder associated with the duplication of a 2 Mb region of 22q11.2. Duplication usually takes in the form of a surpernumerary bisatellited isodicentric chromosome, resulting in four copies of the region (represents an inv dup(22)(q11)). CES is characterized clinically by the combination of coloboma of the iris and anal atresia with fistula, downslanting palpebral fissures, preauricular tags and/or pits, frequent occurrence of heart and renal malformations, and normal or near-normal mental development. Belongs to the metallo-dependent hydrolases superfamily. Adenosine and AMP deaminases family. ADGF subfamily.