TABLE 2.

Effect of ionic strength at pH 5.5 on the activities of purified wild-type PG8fn and its mutants

Enzyme	Relative activity (%) ina:
	McIlvaine buffer (mM)b			Sodium acetate buffer (mM)c
	100	50	10	200	100	50	10
PG8fn	100.0 ± 2.5	133.1 ± 1.9	95.8 ± 0.7	100.0 ± 2.6	43.8 ± 1.9	41.7 ± 0.8	33.1 ± 1.2
D244A mutant	100.0 ± 2.4	109.8 ± 0.9	52.0 ± 1.9	100.0 ± 1.6	48.6 ± 3.1	35.5 ± 2.3	27.7 ± 2.2
D299R mutant	100.0 ± 2.3	106.6 ± 2.2	59.9 ± 1.3	100.0 ± 2.5	67.2 ± 1.0	56.1 ± 1.5	32.1 ± 2.2
D244A/D299R mutant	100.0 ± 2.4	126.2 ± 2.2	96.1 ± 1.0	100.0 ± 0.9	48.4 ± 0.6	43.7 ± 2.0	18.5 ± 0.3

^aRelative activity is defined as the percentage of enzymatic activity toward polygalacturonic acid against that in 100 mM McIlvaine buffer or 200 mM sodium acetate buffer (pH 5.5) at 45°C and is shown as the mean ± standard deviation (n = 3).

^bThe concentration of McIlvaine buffer was based on the amount of citric acid.

^cThe concentration of sodium acetate buffer was based on the amount of sodium acetate.