Cytokinin-activating enzyme working in the direct activation pathway. Phosphoribohydrolase that converts inactive cytokinin nucleotides to the biologically active free-base forms. H2O + N(6)-(dimethylallyl)adenosine 5'-phosphate = D-ribose 5-phosphate + N(6)-dimethylallyladenine 9-ribosyl-trans-zeatin 5'-phosphate + H2O = D-ribose 5-phosphate + trans-zeatin Optimum pH is 6.5. Expressed in roots and shoots. Detected in the vascular tissues of roots, cotyledons, leaves and pistils, in the shoot apical meristem and in immature flowers. Belongs to the LOG family.