Enzymatic Degradation of Adenosine Triphosphate to Adenine by Cabbage Leaf Preparations.

Abstract

The soluble cytoplasmic fraction of cabbage leaf homogenates contains enzymes which readily degrade ATP to adenine. The pathway of breakdown appears to proceed by means of an apyrase reaction to AMP followed by a relatively slow dephosphorylation to adenosine and then a rapid hydrolysis to adenine. Two apyrases have been found in the cytoplasm. One has an acid pH optimum at 5 and requires no added metal ion. The other has optimum activity at pH 8.7 and a requirement for Mg++. Associated with each apyrase is the ability to split inorganic pyro-phosphate. A very active hydrolytic adenosine ribosidase, nucleotide pyrophosphatase, ribonuclease and acid phosphatase are also easily demonstrated in the cytoplasmic preparation. Particulate material isolated from the leaf homogenate by differential centrifugation also contains an enzyme capable of degrading ATP to AMP.