Phosphodiesterase-phosphomonoesterases from Fusarium moniliforme
V. Mode of Action on Various Nucleotides
1974 年 76 巻 1 号 p. 81-89
詳細
1974 年 76 巻 1 号 p. 81-89
1. The rates of liberation of inorganic phosphate from eleven ribonucleoside monophosphates by Fusarium phosphodiesterase-phosphomonoesterase were determined. Adenosine 3'-phosphate, guanosine 3'-phosphate, and cytidine 3'-phosphate are hydrolyzed at high rates, whereas guanosine 5'-phosphate, cytidine 2'-phosphate, and uridine 5'-phosphate are hardly cleaved.
2. All the ribonucleoside monophosphates competitively inhibit the hydrolysis of p-nitrophenyl phosphate by the enzyme, with the exceptions of adenosine 5'-phosphate, guanosine 5'-phosphate, and cytidine 2'-phosphate, which are noncompetitive inhibitors. The apparent slope and intercept inhibition constants for each of the nucleotides were determined. Uridine 3'- and 5'-phosphates have particularly large values of the slope inhibition constant.
3. The rates of liberation of inorganic phosphate by the enzyme from eight ribonucleoside cyclic monophosphates were determined; those from adenosine 2', 3'-cyclic phosphate and guanosine 2', 3'-cyclic phosphate are high; and those from the four 3', 5'-cyclic phosphates are low. No intermediary phosphomonoester was detected in the course of hydrolysis of the cyclic phosphates, except for guanosine 3', 5'-cyclic phosphate, uridine 2', 3'-cyclic phosphate, and uridine 3', 5'-cyclic phosphate. These three yielded guanosine 5'-phosphate, uridine 3'-phosphate, and uridine 5'-phosphate, respectively, as intermediates.
4. Uridylyl-(3'-5')-adenosine was hydrolyzed by the enzyme into uridine, adenosine, and inorganic phosphate without release of any intermediary phosphomonoester. Adenylyl-(3'-5')-uridine, on the other hand, was cleaved into adenosine and uridine 5'-phosphate.
5. The terminal phosphate of adenylyl-(3'-5')-guanosine 3'-phosphate was eliminated rapidly by the enzyme, and the resulting dinucleoside monophosphate was then split into adenosine and guanosine 5'-phosphate. Cytidylyl-(3'-5')-guanosine 3'-phosphate and uridylyl-(3'-5')-guanosine 3'-phosphate behaved in much the same way, except that the splitting of the last dinucleotide was slower than those of the other two.
6. These results were interpreted in the light of the previously proposed mechanism for the action of phosphodiesterase-phosphomonoesterase.
