Table 1.

Kinetic parameters of AspATs for branched and acidic substrates, pH 8.0, 25°C

Substrate	WT*			AV5A-7			AV5A-76
	kcat (s−1)	Km (mM)	kcat/Km (s−1 M−1)	kcat (s−1)	Km (mM)	kcat/Km (s−1 M−1)	kcat (s−1)	Km (mM)	kcat/Km (s−1 M−1)
l-Valine	—†	—†	<1 × 10−3	46 (6)	420 (70)	110	—†	—†	14 (0.2)
l-Isoleucine	—†	—†	<1 × 10−3	—†	—†	6.6 (0.09)	—†	—†	0.5 (0.005)
l-Leucine	—†	—†	2.4	160 (90)	120 (10)	1.3 × 103	—†	—†	160 (1)
2-Oxovaline‡	5.7 (0.1) × 10−3	100 (3)	0.057	28 (1)	3.8 (0.3)	7.4 × 103	60 (4)	33 (4)	1.8 × 103
2-Oxoisoleucine‡	3.3 (0.3) × 10−3	52 (9)	0.063	220 (20)	48 (4)	4.6 × 103	230 (20)	170 (20)	1.4 × 103
2-Oxoleucine‡	1.2 (0.03)	43 (1)	28	140 (6)	3.4 (0.3)	4.1 × 104	290 (10)	19 (2)	1.5 × 104
l-Aspartate	550	4.5	1.2 × 105	220 (10)	68 (8)	3.2 × 103	70 (2)	11 (0.9)	6.4 × 103
l-Glutamate	700	38	1.8 × 104	—†	—†	380 (6)	120 (9)	220 (20)	550
Oxalacetate	800	0.035	2.3 × 107	650 (70)	0.52 (0.08)	1.3 × 106	1.4 (0.1) × 103	0.46 (0.06)	3.0 × 106
2-Oxoglutarate	600	1.3	4.6 × 105	120 (4)	3.9 (0.3)	3.1 × 104	610 (30)	4.5 (0.4)	1.4 × 105

Numbers in parentheses are the standard deviations. 

^*Data from ref. 18, except for those for branched-chain 2-oxo acids. 

^†Reactions did not show saturation kinetics in the substrate concentrations examined. 

^‡Abbreviations: 2-oxovaline, 2-ketoisovaleric acid; 2-oxoisoleucine, dl-2-keto-3-methyl-n-valeric acid; 2-oxoleucine, 2-ketoisocaproic acid.