Hydrolysis of poly (A) to adenine nucleotides by purified poly (A) polymerase.

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Abstract
Highly purified poly(A) polymerase (polynucleotide adenylyltransferase, EC 2.7.7.19), which synthesizes poly(A) from ATP substrate, can also catalyze hydrolysis of poly(A). The enzyme, designated as poly(A) hydrolase, requires either Mn2+ or Mg2+ for activity. Although AMP is the predominant product of the reaction, ADP and ATP are also formed. The enzyme is a 3''-exonuclease that does not degrade poly(A) associated with poly(A).cntdot.poly(U) helical structure. AMP, ADP and ATP inhibit the hydrolytic reaction. The levels of adenine nucleotides may regulate synthesis and degradation of poly(A), poly(A) itself is a storage form of adenine nucleotides, the hydrolytic reaction is responsible for poly(A) shortening or turnover observed in vivo and the synthetic and hydrolytic activities are functions of the same protein molecule.

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