EN
Adenosine deaminase (ADA) was partially purified 486- and 994- -fold from rat liver mitochondria and cytosol, respectively. Relative molecular mass of the enzymes from both fractions was 34 (KM). Km for adenosine and 2'-deoxy-adenosine were 3.08 x 10~5 M and 3.03 x 10 ~5 M for mitochondrial ADA and 3.12 x 10"5 M and 2.87 x 10~5 M for cytosolic ADA. The enzyme from both subcellular fractions had the maximum activity at pH 7.5 - 8.0, and pi 5.2 and 4.2 for mitochondrial and cytosolic enzyme, respectively. The enzyme was inhibited by erythro-9-(2-hydroxy-3-nonvl)adenine and 2'-deoxycoformycin with A'i 4.4 X 10~7 M and 3.2 x 10 M for mitochondrial ADA and 4.9 X I0~7 M 2.8 x 10"7 M for cytosolic ADA. Among the natural nucleoside and deoxynucleotide derivatives tested, deoxyGTPand UTP inhibited only cytosolic adenosine deaminase by 60% and 40%, respectively.