Peroxidase thermal inactivation

Garcia D, Ortega F, Marty JL (1998) Kinetics of thermal inactivation of horseradish peroxidase stabilizing effect of methoxypoly(ethylenglycol). Biotechnol Appl Biochem 27 49-54... 

All Class II and III plant peroxidases have two calcium binding sites, one proximal and one distal to the heme plane (see Figure 18B and C). These divalent cations appear to be vital for efficient peroxide catalysis by maintaining the structural integrity of the heme active site and directing the location of the second oxidizing equivalent derived from peroxide. A series of mutagenic studies with LIP and MnP ascertain that the calcium ions for these two peroxidases are released upon thermal inactivation [184-186]. The loss of these ions results in perturbations of the coordi-... 

SL Timofeevski, SD Aust. Kinetics of calcium release from manganese peroxidase during thermal inactivation. Arch Biochem Biophys 342(1) 169-175, 1997. 

Horse-radish peroxidase has been treated with acetic, butyric, valeric, enanthic, and succinic anhydrides of mono- and di-carboxylic acids, and with picrylsulphonic acid. ° The effects of these modifications on catalytic activity, rates of irreversible thermal inactivation, and absorption and c.d. spectra were studied. The degree of modification rather than the nature of the modifier was found to be responsible for the major effect on the macromolecular conformation and thermostability of the enzyme after modification. 

BS Chang, KH Park, DB Lund. Thermal inactivation kinetics of horseradish peroxidase. J Food Sci 53 920-923 (1988). 

Tan, T.-C., Cheng, L.-H., Bhat, R., Rusul, G., Easa, A. M. (2014). Composition, physicochemical properties and thermal inactivation kinetics of polyphenol oxidase and peroxidase from coconut (Cocos nucifera) water obtained from immature, mature and overly-mature coconut. Food Chemistry, 142(0), 121-128. doi http //dx.doi.org/10.1016/ j.foodchem.2013.07.040... 

Lipase and alkaline phosphatase in milk are ther-molabile (Fig. 2.37), whereas acid phosphatase is relatively stable. Therefore, alkaline phosphatase is used to distinguish raw from pasteurized milk because its activity is easier to determine than that of lipase. Of all the enzymes in the potato tuber (Fig. 2.38), peroxidase is the last one to be thermally inactivated. Such inactivation patterns are often found among enzymes in vegetables. In such cases, peroxidase is a suitable indicator for controlling the total inactivation of all the enzymes e. g., in assessing the adequacy of a blanching process. However, newer developments aim to limit the enzyme inactivation to... 

Fig. 2.37. Thermal inactivation of enzymes of milk, 1 Lipase (inactivation extent, 90%), 2 alkaline phosphatase (90%), 3 catalase (80%), 4 xanthine oxidase (90%), 5 peroxidase (90%), and 6 acid phosphatase...

Table 16.28. Thermal inactivation of lipoxygenase and peroxidase in peanuts...

Thermal Inactivation of Peroxidase. To study thermostability of spinach peroxidase without the influence of cellular components, isolated peroxidase was heat treated in 0.1 M phosphate buffer (pH 6.0). The thermal inactivation curves are presented in Figure 6 and they showed biphasic kinetic curves m the range of 60-70 C. The spinach suspension and the extract (Figure 6b and c) also exhibited biphasic curves similar to that of isolated peroxidase (Figure 6a). The thermodynamic data were siunmarized in Table m. The results indicated that isolated peroxidase was more thermostable than those in the suspension or in the extract in the range of 50-80 t). However, z-value was 13 t) for isolated peroxidase which was less than those ( 18 TO) for both of the enzymes in the suspension or tiie extract The results showed that peroxidase isolated fix>m spinach responded differently to heating than the enzymes in the spinach extract or suspension. In Table IV, heat stabilities of peroxi-... 

Application of Kinetic Data to Thermal Processing. In most studies on ttiermal inactivation of indicator enzymes including peroxidase, lipoxygenase, and LAHase, reaction rate constants and thermodynamic parameters have been determined on the assumption that thermal inactivation of the enzymes follows first order reaction kinetics (22). However, a deviation from first order kinetics is generally observed fipm the residual activity curve. This deviation has been explained by several mechanisms, including the formation of enzyme aggregate with different heat stabilities, the presence of heat stable and labile enzymes, and the series type inactivation kinetics. 

Terefe, N.S., Yang, Y.H., Knoerzer, K., Buckow, R., and Versteeg, C. (2009) High pressure and thermal inactivation kinetics of polyphenol oxidase and peroxidase in strawberry puree. Innovative Food Science and Emerging Technologies, 11, 52-60. 

Forsyth et al. (16) studied the thermal performance of peroxidase at 75°C and obtained a D-value range from 0.01 to 7.38 min for the native enzyme and between 0.096 and 18.96 min for the partially inactivated enzyme. 

Several studies have demonstrated the improved stability of peroxidases when they were subjected to immobilization. Akhtar and Husain observed that bitter gourd peroxidase (BGP) was able to remove higher percentage of phenols over a wider range of pH when immobilized on a bioaffinity support [37]. Sasaki et al. highlighted an improvement of thermal stability of MnP immobilized on FSM-16 mesoporous material [59]. Furthermore, some other studies demonstrated a protective effect of peroxidase immobilization against inactivation by H202 [7, 20]. The different behavior of immobilized peroxidases with respect to soluble ones points out the necessity of an optimization of the process conditions when immobilized enzyme is used. Nevertheless, the possible improvement in stability should balance the usual decrease in kinetic rates, due to substrate transfer limitations to reach the enzyme inside the support. 

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