PHOSPHODIESTERASE-I IN CULTURED-CELLS OF MENTHA-ARVENSIS

Alkaline phosphodiesterase I (5'-nucleotide phosphodiesterase, EC 3.1. 4.1) in cultured cells of Mentha arvensis, was purified about 75-fold by ammonium sulphate fractionation and three chromatographic steps. Th e optimum pH of the enzyme was 9.5. Its M(r) was estimated by gel filt ration to be cn 105000. The enzyme was strongly inhibited by SH reagen ts and HgCl2. It did not require divalent cations such as Mg2+ or Ca2. It hydrolysed thymidine 5'-p-nitrophenylphosphate but did not act on DNA or RNA. These properties, such as divalent cation requirement and substrate specificity, were different from those of phosphodiesterase I obtained from carrot.