Luminol–hydrogen peroxide chemiluminescence produced by sweet potato peroxidase

Anionic sweet potato peroxidase (SPP; Ipomoea batatas) was shown to efficiently catalyse luminol oxidation by hydrogen peroxide, forming a long-term chemiluminescence (CL) signal. Like other anionic plant peroxidases, SPP is able to catalyse this enzymatic reaction efficiently in the absence of any enhancer. Maximum intensity produced in SPP-catalysed oxidation of luminol was detected at pH 7.8–7.9 to be lower than that characteristic of other peroxidases (8.4–8.6). Varying the concentrations of luminol, hydrogen peroxide and Tris buffer in the reaction medium, we determined favourable conditions for SPP catalysis (100 mmol/L Tris–HCl buffer, pH 7.8, containing 5 mmol/L hydrogen peroxide and 8 mmol/L luminol). The SPP detection limit in luminol oxidation was 1.0 × 10−14 mol/L. High sensitivity in combination with the long-term CL signal and high stability is indicative of good promise for the application of SPP in CL enzyme immunoassay. Copyright © 2006 John Wiley & Sons, Ltd.