Study of Properties and Activity of Cytidine Deaminase in Serum and Erythrocytes by a Colorimetric Method

A colorimetric method was developed for determination cytidine deaminase activity in serum and erythrocyte haemolysate. This method based on estimation the amount of ammonia produced from conversion of cytidine into uridine. The optimum conditions of the enzyme using this method were obtained.
The result showed that maximum activity of cytidine deaminase by the method above in serum and erythrocyte haemolysate was obtained using (100 mM) and (200 mM) of buffer solution sodium phosphate for serum and erythrocyte respectively at pH (7.5) and (2mM) cytidine as a substrate and (75L) serum and (50 L) erythrocyte haemolysate as a source of enzyme for (45 min) and (30 min) serum and erythrocytes haemoly sate at (35 C).
Moreover, the results of the study also predicted that presence of some amino acids such as histidine, glutamic in the reaction solution activate the enzyme activity, while some metal salts such as MgCl2, CoCl2, KCl and CuCl2 inhibited the activity.