Research Article
Saeidian Shahriar
Abstract
Peroxidases (EC 1.11.1.7. ) belong to a large family of enzymes that are ubiquitous in fungi, plants, and vertebrates. The enzyme usually contains a ferri proto porphyrin IX prosthetic group and oxidizes several substrates in the presence of hydrogen peroxide Peroxidase, extracted from cherry tomatoes was isolated by ammonium sulfate precipitation technique and purified by ion exchange chromatography. The crude enzyme having 36 U/mL activity and 2.4 U/mg specific activity was subjected to ammonium sulfate precipitation technique for partial purification and the resulted activity and specific activity were 28 U/mL and 7.3 U/mg respectively. After ion exchange chromatography through DEAE-cellulose, fraction between 40-60 exhibited maximum activity of 24 U/mL and specific activity of 15 U/mg. The enzyme under discussion was found to be quite active with optimum temperature of 45oC. Optimum pH for the enzyme was 5.5. Thermal treatment of crude extract of cherry tomatoes peroxidase was more stable at pH 5.5.Results showed optimum temperature is 45 oC for enzyme. Like most chemical reactions, with increase of temperature from 27 ºC, gradually, activity of peroxidase increased so; we reached to maximum of activity at 45 ºC (180%). It was found that enzyme followed the Michealis-Menton mechanism and 42 units/mg.protein and 12mM were the calculated values for Vmax and Km in precence of various concentrations of guaiacol and constant concentration of H2O2. The results showed that cherry tomatoe peroxidase was a thermostable enzyme. After 40 min at 55°C, the remaining activity was 40%.