. "Cytosolic uridine phosphorylase (isoforms UPP1 and UPP2) catalyzes the reversible reactions of uracil with ribose 1-phosphate or deoxyribose 1-phosphate to yield uridine or deoxyuridine and orthophosphate (Watanabe and Uchida 1995; Johansson, 2003). The active form of UPP1 is a dimer (Rooslid et al. 2009)."^^ . . . . . . . . "uracil + (deoxy)ribose 1-phosphate <=> (deoxy)uridine + orthophosphate [UPP]"^^ . "2.4.2.3"^^ . . . . . . . .