PURIFICATION AND SOME PROPERTIES OF ADENOSINE (PHOSPHATE) DEAMINASE FROM THE LIVER OF THE SQUID TODARODES PACIFICUS

An enzyme that catalyzed the deamination of adenosine 3'-phenylphospho nate was purified from squid liver to homogeneity as judged by SDS-PAG E. The molecular weight of the enzyme was estimated to be 60,000 by SD S-PAGE and 140,000 by Sephadex G-150 gel filtration. The enzyme deamin ated adenosine, 2'-deoxyadenosine, 3'-AMP, and 2',3'-cyclic AMP, but n ot adenine, 5'-AMP, 3',5'-cyclic, AMP, ADP, or ATP. The apparent K-m a nd V-max at pH 4.0 for these substrates were comparable (0.11-0.34 mM and max 179-295 pmol min(-1) mg(-1), respectively). The enzyme had max imum activity at pH 3.5-4.0 for adenosine 3'-phenylphosphonate, at pH 5.5 for adenosine and 2'-deoxyadenosine, and at pH 4.0 for 2',3'-cycli c AMP and 3'-AMP when the compounds were at concentration of 0.1 mM. T he K-m at 4.0 and 5.5 for each substrate varied, but the V-max were in variant. These results indicated that the squid enzyme was a novel ade nosine (phosphate) deaminase with a unique substrate specificity.