. Author manuscript; available in PMC: 2019 Jun 15.

Published in final edited form as: ACS Chem Biol. 2018 May 17;13(6):1610–1620. doi: 10.1021/acschembio.8b00230

Table 2.

Persulfide Reductase Activity of CoAPR towards LMW Persulfide Substrates in the Presence of FAD and Either NADH^a or NADPH^b and in the Presence of Excess Product or Other Persulfides

LMW persulfide substrate	reaction additives	K_m (μ M)	V_max (μ mol min⁻¹ mg⁻¹)	k_cat (s⁻¹)	k_cat/K_m (× 10⁴ M⁻¹ s⁻¹)	k_cat ratio^f
CoASSH^a	none	111 ± 23	4.9 ± 0.4	4.9 ± 0.4	4.4 (±1.0)	1.0 ± 0.12
CoASSH^b	NADPH	N.D.^c	0.37 ± 0.12	0.31 ± 0.07	N.D.	0.06 ± 0.24
CoASSH^a	200 μM CoASH	111^e	4.0 ± 0.3	4.0 ± 0.3	N.D.	0.82 ± 0.11
CoASSH^a	1 mM CoASH	111^e	2.2 ± 0.2	2.2 ± 0.2	N.D.	0.45 ± 0.12
CoASSH^a	200 μM CysSSH	111^e	5.3 ± 0.4	5.2 ± 0.4	N.D.	1.1 ± 0.11
CoASSH^a	1 mM CysSSH	111^e	3.4 ± 0.4	3.4 ± 0.4	N.D.	0.69 ± 0.14
CysSSH^a,^d	none	270 ± 568	0.11 ± 0.11	0.11 ± 0.11	N.D.	0.022 ± 1.0
GSSH^a,^d	none	150 ± 293	0.08 ± 0.06	0.08 ± 0.06	N.D.	0.016 ± 0.75

Conditions: 100 nM CoAPR (protomer), 100 nM FAD, 100 μM NADH, 25 mM Tris-HCl, 200 mM NaCl, pH 8.0, 25 °C.

Conditions: 100 nM CoAPR (protomer), 100 nM FAD, 100 μM NADPH, 25 mM Tris-HCl, 200 mM NaCl, pH 8.0, 25 °C.

N.D., not determined.

Very low activity, making it difficult to measure K_m and V_max accurately.

K_m fixed to 111 μM during data fitting.

Relative k_cat determined relative to k_cat for CoASSH substrate and NADH cofactor, first row of table.