Partial characterization of peroxidase from the leaves of thymbra plant (Thymbra spicata L. var. spicata).

摘要

Peroxidase (EC 1.11.1.7; donor: hydrogen-peroxide oxidoreductase) catalyses the oxidation of various electron donor substrates (e.g. phenols, aromatic amines). In this study, peroxidase was extracted from the herb, Thymbra spicata L. var. spicata, and partially purified by (NH4)2SO4 precipitation and dialysis. The substrate specificity of peroxidase was investigated using 2,2'-azino-bis(3-ethylbenz-thiazoline-6-sulfonic acid) (ABTS), o-dianisidine, o-phenylenediamine, catechol and guaiacol as substrates. Furthermore, the effects of buffer concn., pH, temp. and thermal inactivation on enzyme activity were also studied. Results showed that: the best substrate was o-dianisidine, followed by ABTS, catechol, guaiacol and o-phenylenediamine; the best buffer concn. were 40mM for o-dianisidine and catechol, 10mM for ABTS and guaiacol and 100mM for o-phenylenediamine; the optimum pH was 2.5 for ABTS and o-phenylenediamine, 6.0 for o-dianisidine and 7.0 for catechol and guaiacol; the optimum temp. was 20 degrees C for catechol, 40 degrees C for ABTS, guaiacol and o-dianisidine, and 50 degrees C for o-phenylenediamine; and enzyme activity during thermal inactivation experiments was enhanced by increase in temp. with o-dianisidine as a substrate, while its activity decreased with o-phenylenediamine.