کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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4365492 | 1301761 | 2011 | 9 صفحه PDF | دانلود رایگان |
Two extracellular humic acids peroxidases called HaP1 and HaP2 were isolated from the Streptomyces sp. strain AM2 and, based on MALDI-TOF MS analysis. The purified enzymes were determined as monomers with molecular masses of 40,351.11 and 25,175.19 Da, respectively. The N-terminal amino acid sequences of HaP1 and HaP2 were identified, and their optimum pH values were determined as 6 and 7.5, respectively. Standard 2,4-dichlorophenol (2,4-DCP) assays showed that both enzymes had maximal activity at 55 °C. HaP2 was stable at 55 °C for more than 24 h and had a half-life of 90 min at 65 °C. Although the catalytic properties of HaP1 and HaP2 were nearly identical, their stabilities and Reinheitzahl (RZ) values were substantially different. Both peroxidases were found to be heme proteins that catalyzed the oxidation of a wide range of substrates in the presence of hydrogen peroxide (H2O2), with HaP2 exhibiting a broader range of substrate specificity. The characterization of peroxidase activity revealed activity against humic acids, guiacol, 2,4-DCP, l-3,4-dihydroxyphenylalanine, and 2,4,5-trichlorophenol as well as other chlorophenols in the presence of H2O2. However, the inhibition of peroxidase activity by the addition of potassium cyanide and sodium azide also indicated the presence of heme components in the tertiary structure of these enzymes.
Journal: International Biodeterioration & Biodegradation - Volume 65, Issue 3, June 2011, Pages 470–478