... yeast [11] and mammalian [12,13] enzymes that all require the presenceof UTP and/ or ATP to form tetramers. Therefore, theL. lactis CTP synthase is an attractive candidate formechanistic and structure–function ... synthesis was dramatically influenced bythe presence of GTP, and 20 and 41-fold increases in kcatwere obtained with GTP concentrations of 0.1 mM and 1mM, respectively. However, only a modest decrease ... constants in Table 1, and those obtainedfor the glutaminase reaction in the presence of 0.1 mMeachof UTP and ATP-cS (data not shown). Apparently, thevalue of Ka, kcat,1 and kcat,2were similar...