Effect of phosphorylation on the reaction rate of unnatural electrophiles with 2-keto-3-deoxy-6-phosphogluconate aldolase
D-Glyceraldehyde is accepted as an electrophile by 2-keto-3-deoxy-6-phosphogluconate (KDPG) aldolase (EC 220.127.116.11) at 1% the rate of natural substrate, D-glyceraldehyde 3-phosphate. Accordingly, it was expected that addition of a phosphate moiety at C3 or C4 of unnatural aldehydes would enhance their activity as electrophilic substrates. Furthermore, phosphate would act as a useful protecting group during synthetic manipulations of the aldol adduct. A variety of phosphorylated and non-phosphorylated aldehydes were synthesized and evaluated as substrates for KDPG aldolase. Although small variations in reaction rate were observed, phosphorylation failed to provide a universal rate enhancement. Evaluation of substrate kinetic parameters revealed that the high rate of reaction of D-glyceraldehyde 3-phosphate compared to related electrophiles is entirely due to the efficiency of turnover with little change in binding exhibited among various substrates.