TABLE 2

Kinetic parameters for bovine XO metabolism of 6-substituted quinazolinones

R =	K_M^{^a}	V_max^{^b}	V/K^{^c}	KIE^{^d}
	μ M	nmol/s/mg enzyme
OCH₃	85	9	101	N.D.
CH₃	56	121	2161	5.2
H	31	17	548	N.D.
Cl	11	164	14,909	3.0

N.D., not determined.
↵a The concentration at half-maximal velocity. Errors are approximately 10% for each value.
↵b The maximum velocity estimated from the asymptote for the hyperbola. Errors are approximately 10% for each value.
↵c V/K multiplied by 1000.
↵d The isotope effect on V/K determined by taking the ratio of V/K for the proton/deuterium substitution at the site of oxidation from Skibo et al. (1987).