. 2019 Aug 9;9:11576. doi: 10.1038/s41598-019-48091-7

Table 2.

Kinetic parameters of candidate OHB decarboxylases on 2-keto-4-hydroxybutyrate (OHB) and corresponding natural substrates.

Enzyme	Natural substrate^a			2-keto-4-hydroxybutyrate				Specificity^c
Enzyme	V^max [U mg⁻¹]	K_M [10⁻³ M]	V^max/K_M [U mg⁻¹ M⁻¹]^b	V^max [U mg⁻¹]	K_M [10⁻³ M]	K_i [10⁻³ M]	V^max/K_mM [U mg⁻¹ M⁻¹]^b	Specificity^c
Zm-Pdc	49.56 (±1.20)	1.7 (±0.2)	29,416 (±4,625)	0.01 (±0.0003)	0.4 (±0.2)	—	34 (±13)	864
Zm-Pdc W392Q	1.74 (±0.32)	5.2 (±0.3)	335 (±83)	0.02 (±0.004)	0.5 (±0.2)	5.0 (±0.4)	46 (±23)	7
Ll-KdcA	2.66 (±0.17)	2.7 (±0.2)	416 (±43)	0.02 (±0.001)	2.5 (±1.6)	—	9 (±5)	48
Ll-KdcA V461I	2.89 (±0.52)	5.1 (±1.1)	590 (±233)	0.04 (±0.0001)	1.3 (±0.5)	—	31 (±12)	19

Data presented are the mean (±S.D.) of at least two replicates.

^aNatural substrates were used as follows: pyruvate for Zm-Pdc, 3-methyl-2-ketobutyric acid for Ll-KdcA.

^bActivities were estimated in U mg⁻¹ purified protein.

^cSpecificity corresponds to the ratio of (v_max/K_m) between natural substrate and OHB.