Table 3. Kinetic Parameters^a for Hydrolysis by Wild-Type HexD and Various Mutants.

	substrate	KM (mM)	kcat (min–1)	kcat/KM (min–1 mM–1)	relative activity (WT/mutant)
WT	3F4NP-GalNAc	0.172 ± 0.019	122 ± 3.9	708 ± 83	1
WT	PNP-GalNAc	0.0721 ± 0.0048	79.1 ± 1.2	1090 ± 77	1
D148A	3F4NP-GalNAc	0.566 ± 0.068	0.461 ± 0.023	0.815 ± 0.11	868
D148N	3F4NP-GalNAc	1.73 ± 0.27	0.293 ± 0.027	0.169 ± 0.030	4190
E149A	PNP-GalNAc	0.0525 ± 0.0034	36.1 ± 0.52	691 ± 52	1.6
E149A	3F4NP-GalNAc	0.213 ± 0.018	176 ± 4.8	825 ± 74	0.85
E149Q	PNP-GalNAc	0.175 ± 0.031	89.3 ± 4.6	508 ± 94	2.2
H92A	PNP-GalNAc	0.196 ± 0.028	3.09 ± 0.13	15.8 ± 2.4	69

^aCalculated kinetic parameters represent the mean ± SEM of triplicate values.