Preferential inhibition of xanthine oxidase by 2-amino-6-hydroxy-8-mercaptopurine and 2-amino-6-purine thiol

BMC Biochemistry

Table 3 Table showing kinetic parameters of APT and AHMP.

Inhibitor	Substrate	K_m (μM)	Mechanism of inhibition	K_i (μM)	k_cat(min)^-1
APT	Xanthine	2.65 ± 0.02	Competitive	6.61 ± 0.28	114.54 ± 0.24
	6MP	6.01 ± 0.03	Competitive	1.30 ± 0.09	2.85 ± 0.02
AHMP	Xanthine	2.71 ± 0.05	Mixed	5.7 ± 0.48(K_i²) (Competitive) 6.24 ± 0.04 (K_I²) (Non-competitive)	128.57 ± 0.45
	6MP	4.89 ± 0.04	Mixed	0.96 ± 0.01(K_i²) (Competitive) 0.98 ± 0.06 (K_I²) (Non-competitive)	3.64 ± 0.04

The reaction mixture comprised of 1 ml of 0.2 M, sodium phosphate buffer pH 7.4 containing 10 μM of either xanthine or 6MP. The reaction was initiated by the addition of 2.8 U/ml of bovine XOD.
K_i² = Inhibition constant for competitive inhibition mechanism exhibited by AHMP
K_I² = Inhibition constant for non-competitive inhibition mechanism exhibited by AHMP

ISSN: 1471-2091