Feline thymidine kinase 1: molecular characterization and evaluation of its serum form as a diagnostic biomarker

BMC Veterinary Research

Table 3 Kinetic parameters

Substrate	K_M (μM)	V_max (μmol/min/mg)	Efficiency (V_max/K_M)	Hill coefficient (n)
dThd	2.25 ± 0.49	1.84 ± 0.09	0.82 (100)*	1.9
dUrd	22.0 ± 1.57	2.91 ± 0.08	0.13 (16.1)	0.9
5FdU	3.13 ± 0.52	2.02 ± 0.08	0.64 (78.8)	0.6
AZT	1.60 ± 0.28	0.94 ± 0.03	0.59 (72.0)	2.1
TFT	3.54 ± 0.28	1.41 ± 0.02	0.40 (48.7)	1.4
Urd	4850 ± 300	0.53 ± 0.01	0.00011 (0.013)	1.0
dGuo	4690 ± 372	0.14 ± 0.004	0.000031 (0.0038)	1.0
ATP	256 ± 37	1.94 ± 0.14	0.0030	2.2

Kinetic parameters were determined by using a coupled spectrophotometric method at 21 °C. To determine the kinetic parameters for the phosphate acceptors, the ATP concentration was fixed at 1 mM and to determine the kinetic parameters for ATP, the dThd concentration was fixed at 100 μM. The K_M and V_max values were determined by fitting the initial velocity data into the Michaelis-Menten equation. The Hill coefficient (n) was calculated by fitting the initial velocity data into the Hill equation

ISSN: 1746-6148