A uridine diphosphatase from sugar cane

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Abstract
A phosphatase that attacks certain nucleoside 5[image]-diphosphates, but not the corresponding mono- and tri-phosphates, was purified 43-fold from sugar cane storage tissue. The relative activities for the 5[image]-diphosphates of uridine, of inosine, of guanosine, of deoxyguanosine, of cytidine, of thymidine and of adenosine were 1.0, 0.45, 0.38, 0.11, 0.08, 0.06 and 0.0, respectively. The relationship between activity and the structure of substrates is discussed. Added Mg2+ ions increased activity by only 40% but the enzyme was completely inhibited by EDTA. Activity was depressed to some extent by fluoride, inorganic phosphate and Mn2+ ions. The enzyme operated at more than 50% of its maximum rate between pH 5.8 and 8.9. The Michaelis constant for UDP was less than 0.1 m[image]. Phosphatase preparations that attacked UDP much more rapidly than they did either UMP or UTP were obtained from a number of other plant tissues.