Studies on nucleotides and related compounds in plants. II. An adenyl-cleaving enzyme system in potato tubers

Adenyl-cleaving activity was demonstrated in clarified potato juice. A stock freezedried enzyme preparation, obtained after (NH₄)₂SO₄ fractionation, hydrolysed adenosine and deoxyadenosine but had no effect on other possible nucleoside substrates including cytidine, deoxycytidine, guanosine, deoxyguanosine, inosine, hypoxanthosine, uridine and thymidine. The rate of adenine release for adenosine was some 60% of that for deoxyadenosine under the conditions of the digest. AMP, ADP, ATP and dAMP were all susceptible to hydrolysis releasing adenine. Evidence is produced to show that dephosphorylation is a necessary prerequisite to adenine release. The adenine nucleosidase has an optimum pH 4.1–4.6 and an apparent temperature optimum of 50 °C.