Phosphodiesterase I in cultured cells of Mentha arvensis

Abstract 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. The optimum pH of the enzyme was 9.5. Its M r was estimated by gel filtration to be ca 105 000. The enzyme was strongly inhibited by SH reagents and HgCl 2 . It did not require divalent cations such as Mg 2+ or Ca 2+ . 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.