TABLE 1.

Kinetic parameters for Axe2 activity on different synthetic substrates at pH 6.0 and 30 °C

Michaelis-Menten constants were obtained from initial rates at different substrate concentrations and following analysis using GRAFIT 5.0.1. The reactions contained 450 μl of citrate phosphate buffer (pH 6.0) with the enzyme in the appropriate concentration (1.5 × 10⁻⁴ to 3.75 × 10⁻⁵ mm final concentrations in the reactions) and 350 μl of substrates dissolved in either isopropyl alcohol or Me₂SO. Control mixtures containing all of the reactants except the enzyme were used to correct for spontaneous hydrolysis of the substrates.

Substrate	pKa	kcat	Km	kcat/Km	Specific activity
		s−1	mm	mm−1s−1	mmol min−1mg−1
Phenyl acetate	9.99	77	7	11	187
2-Naphthyl acetate	9.51	190	9	20	460
4-Methylumbelliferyl acetate	7.53	123	3	41	297
4-Nitrophenyl acetate	7.18	31	27	1	72