TABLE 2.

Isotope effects

Enzyme	kcat	DV	DV/Km(NAD+)	D2OV	D2OV/Km(NAD+)	Rate-limiting step(s)
	s−1
Human IMPDH2	0.31 ± 0.01a	1.0 ± 0.1a	2.5 ± 0.2a	1.8 ± 0.1a	NDb	Hydrolysis
AnImdA	0.74 ± 0.06c	1.0 ± 0.3	2.5 ± 0.6	1.6 ± 0.1	1.1 ± 0.1	Hydrolysis
PbIMPDH-A	0.70 ± 0.08c	1.6 ± 0.2	1.6 ± 0.3	1.5 ± 0.1	1.2 ± 0.1	Hydride transfer/hydrolysis
PbIMPDH-B	0.41 ± 0.02c	2.5 ± 0.3	3.4 ± 0.2	1.1 ± 0.1	0.9 ± 0.2	Hydride transfer
PbIMPDH-B R429Ad	(4.0 ± 0.3) × 10−4	ND	ND	4.4 ± 0.4	ND	Hydrolysis

^a Values are from Ref. 21.

^b ND, no data.

^c Values are from Ref. 5.

^d This is residue 449 in PbIMPDH-B numbering.