Table 2.

K_i values and types of inhibition

Enzyme	Substrate	Inhibitor	Electron acceptor	Detection wavelength	Types of inhibition	Ki (μM)
XO	Xanthine	Oxypurinol	O2	295 nm	Competitive	6.35 ± 0.96
XDH	Xanthine	Oxypurinol	NAD+	295 nm	Competitive	4.60 ± 0.87
XDH	Hypoxanthine	Oxypurinol	NAD+	340 nm	Competitive	3.15 ± 0.22
XOR	Xanthine	Oxypurinol	PMS	550 nm	Competitive	1.65 ± 0.24
XOR	Hypoxanthine	Oxypurinol	PMS	550 nm	Competitive	1.29 ± 0.14
XOR	Xanthine	Febuxostat	PMS	550 nm	Mixed	0.64 ± 0.12 (nM)
XOR	Hypoxanthine	Febuxostat	PMS	550 nm	Mixed	0.72 ± 0.19 (nM)

Values reported are the mean ± S.E.