Guanine Deaminase (GDA)

Guanine deaminase (GDA) catalyzes the hydrolytic deamination of guanine, producing xanthine and ammonia.Cypin localizes to both pre- and postsynaptic sites, is enriched in dendritic shafts, cofractionates, and associates with membrane-associated guanylate kinase proteins (PSD95/93 and SAP97/102) in the synaptic plasma membranes and vesicles. Cypin also occurs in the epithelial cells of the small intestine, highest at the tips of the intestinal villi, and exclusively at the basal membrane. GST fusion experiments showed that cypin binding to PSD95 occurs through a C-terminal consensus sequence and requires PDZ domains 1 and 2. Overexpression of cypin in rat hippocampal neurons specifically perturbs postsynaptic trafficking of PSD95 and SAP102 , an effect not produced by overexpression of other PDZ ligands.