Table 3.

Enzymatic assay of ferric iron reductase activity for the purified enzyme of M. magnetotacticum

Substrate(s)Activitya(%)Km (μM)
+substrate−substrate
Reductants
 NADH1.59b (100)01.3
 NADPH0.26 (16)NA119.3
 Glutathione0NAND
Flavin
 FMN1.59b (100)0.18 (11)0.035
 FAD0.28 (18)NAND
Iron source
 Ferric citrate1.59b (100)014.5
 Ferric quinate0.36 (23)NAND
  • a Determined by measuring the increase in the A 562, using a Δɛ562 value of 28 mM−1 cm−1. NA, not assayed. ND, not determined.

  • b Standard conditions: 20 mM sodium phosphate buffer (pH 7.0), 100 μM NADH, 1 μM FMN, 1 mM ferrozine, 200 μM ferric citrate.