Table 2.

Kinetic constants of Thermoplasma acidophilum isopentenyl phosphate kinase (THA IPK) mutants for the phosphorylation of isopentenyl phosphate (IP), geranyl phosphate (GP), and farnesyl phosphate (FP). Measurements were performed at a saturating concentration of ATP (250 μM).

	kcat (s-1)	KM(μM)	kcat/KM(M-1s-1)
Wild-type THA IPK
GP	0.05	4.7 (± 1.3) × 103	10.0
FP	not determined	not determined	not determined
IP	8.0	4.4 (± 0.5)	1.8 × 106
YV73V130I
GP	1.1 (± 0.1)	2.4 (± 0.3) × 103	4.7 × 102
FP	0.6 (± 0.1)	1.8 (± 0.1) × 103	3.4 × 102
IP	2.6 (± 0.1) × 10-3	5.3 (± 0.8) × 103	0.5
YV73I
GP	4.1 (± 0.2)	3.5 (± 0.3) × 103	1.2 × 103
FP	1.4 (± 0.1)	1.6 (± 0.3) × 103	8.8 × 102
IP	1.0 (± 0.6) × 10-2	7.9 (± 0.1) × 103	1.3
YV130I
GP	10.1 (± 0.7)	8.0 (± 1.1) × 103	1.3 × 103
FP	1.4 (± 0.1)	1.5 (± 0.2) × 103	9.9 × 102
IP	4.8 (± 0.3) × 10-3	5.7 (± 0.9) × 103	0.9
V73V130I
GP	2.8 (± 0.5)	9.5 (± 2.7) × 103	3.0 × 102
FP	not determined	not determined	not determined
IP	1.1 (± 0.1) × 10-2	4.2 (± 0.7) × 103	2.6