Table 2.

Library of Alternative Substrates: Observed Activity, Inhibition, and Calculated Oxidation Potentials for Analogues of PCA

substrate	activity observed	% activitya	% inhibitionb	Eabsolute oxidation (eV)
(HPCA) Homprotocatechuate	Y	0.2		5.40
4-methylcatechol	N		28	5.71
PCA	Y	100		5.82
catechol	Y	0.17		5.88
3,4-dihydroxybenzamide	Y	33		6.11
3,4-dihydroxybenzaldehyde	N			6.19
3,4-dihydroxybenzonitrile	Y	0.04		6.30
4-nitrocatechol	N		31	6.46
gallate	Y	24
3-O-methylgallate	Y	3
2,3,4-trihydroxybenzoic acid	N		95
2,3-dihydroxybenzoic acid	N		36
3-methoxycatechol	N		26

^aMeasured with 5 mM substrate in air-saturated 50 mM Tris buffer at 25 °C, and pH 7.5. Calculated as a percentage of the activity of LigAB with 5 mM PCA.

^bMeasured with 500 μM PCA and 1 mM inhibitor in air-saturated 50 mM Tris buffer at 25 °C and pH 7.5. Calculated as a percentage of the activity of LigAB with 500 μM PCA with no inhibitor present.