FIGURE 6.
Phosphomonoesterase activity of GP12 during WTA analog degradation. A, radioactive chromatograms for products from overnight (18 h) reactions of GP12 with [14C]glycerol lipid ϕ.40 analogs, after separation by anion exchange HPLC. Control reactions lacking enzyme showed no evidence of non-enzymatic degradation. B, time course for Pi generation from degradation of lipid ϕ.40 analogs. Reaction mixtures contained 70 μm lipid ϕ.40 analog and 1 μm GP12 or 70 μm glycosylated lipid ϕ.40 analog and 0.25 μm GP12. Data points are the mean from two independent experiments. C, summary of the reactions catalyzed by GP12 with WTA substrates. (i) a glycerophosphoglycerol-type product is released as the alcohol leaving group from GP12 phosphodiester hydrolysis. R1 = H or [glycerol 3-phosphate]n; R2 = H or glucose. (ii) GP12 hydrolyzes the phosphomonoester product from preceding phosphodiester hydrolysis to release Pi.