The PGM3 gene encodes the major phosphoribomutase in the yeast Saccharomyces cerevisiae

► Pgm1, Pgm2, and Pgm3 accept glucose-1-P and ribose-1-P as substrates in vitro. ► Ribose-1-P is formed in vivo upon perturbation of energetic equilibrium. ► Ribose-1-P only hyper-accumulates in mutants carrying a deletion in PGM3. ► Pgm3 is the major phosphoribomutase in yeast.