Dependence of heme accessibility in horseradish peroxidase on Ca2+

Coates, A.; Cook, Marcus P.; Feezor, Robert J.; Schuh, Merlyn D.

doi:10.1016/s0162-0134(98)10064-8

Cited by 10 publications

(12 citation statements)

References 23 publications

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“…Inhibition of cantaloupe peroxidase activity by tiron in this study is, however, more likely to result from its binding ability with peroxidase because other free radical scavengers and initiators had no effect on enzyme activity. Our results also indicate that CaCl 2 , a common additive in the blanching of fruits and vegetables [33] is unlikely to increase peroxidase activity as reported for horseradish [34,35], wheat [36] and sweet potato [37]. Peroxidases are indices of ripening and senescence [1].…”

Section: Resultssupporting

confidence: 62%

Cantaloupe melon peroxidase: Characterization and effects of additives on activity

Lamikanra¹,

Watson

2000

Nahrung

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Peroxidase in cantaloupe melon (Cucumis melo L. var. reticulatus Naud.), a fruit commonly fresh cut processed, was characterized to determine reaction pathway, optimal conditions for activity and effect of some additives on enzymatic action. Mn2+, CaCl2, NaNO2 and kinetin had partial inhibitory effects on enzyme activity. Activity was effectively inhibited by compounds capable of chelating peroxidase heme iron such as diethyldithiocarbamate and tiron, but unaffected by EDTA. Free radical scavenger, superoxide dismutase, also had no effect on reaction velocity. Enzymatic action was consistent with that of ascorbate peroxidase based on the relatively higher affinity for ascorbate over guaiacol. Optimum activity temperature was 50-55 degrees C. The enzyme was stable at temperatures below 40 degrees C and at 50 degrees C for up to 10 min. Over 90% of total activity was lost at 80 degrees C within 5 min. Broad pH optima, 5.5-7.5 at 50 degrees C and 6-7 at 30 degrees C, were obtained. Peroxidase activity in cantaloupe was higher than those in strawberry (Fragaria ananassa Duch.) and lettuce (Lactuca sativa L.), suggesting a relatively high oxidative stress in fresh cut cantaloupe. The potential use of ascorbate as an additive in fresh cut cantaloupe melon was demonstrated by its ability to preserve color in minimally processed fruits for 25 days at 4 degrees C, possibly as a result of an enhanced antioxidative action of the ascorbate-peroxidase complex and trace metal ion cofactors.

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Section: Resultssupporting

confidence: 62%

Cantaloupe melon peroxidase: Characterization and effects of additives on activity

Lamikanra¹,

Watson

2000

Nahrung

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“…Also, since Asp 230 bonds directly to the proximal Ca 2+ , better hydrogen bonding by the substituting Asn may strengthen the Ca 2+ binding pocket [45]. Consolidation of this pocket may delay loss of the proximal calcium ion, which is known to play a pivotal role in HRP stabilisation [46]. This is reflected in the increased thermal (1.8-fold, Table 1) and solvent (DMF, 3.4-fold; Table 1 [47].…”

Section: Discussionmentioning

confidence: 99%

Effects of mutations in the helix G region of horseradish peroxidase

Ryan¹,

Ó’Fágáin²

2008

Biochimie

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Summary.Horseradish Peroxidase (HRP) has long attracted intense research interest and is used in many biotechnological fields, including diagnostics, biosensors and biocatalysis. Enhancement of HRP catalytic activity and/or stability would further increase its usefulness. Based on prior art, we substituted solvent-exposed lysine and glutamic acid residues near the proximal helix G (Lys 232, 241; Glu 238, 239) and between helices F and F' (Lys 174). Three single mutants (K232N, K232F, K241N) demonstrated increased stabilities against heat (up to two-fold) and solvents (up to four-fold). Stability gains are likely due to improved hydrogen bonding and space-fill characteristics introduced by the relevant substitution. Two double mutants showed stability gains but most double mutations were non-additive and non-synergistic.Substitutions of Lys 174 or Glu 238 were destabilising. Unexpectedly, notable alterations in steady-state V m /E values occurred with reducing substrate ABTS (2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)), despite the distance of the mutated positions from the active site.

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“…This approach differs from the earlier described HRP derivatives, where the iron central atom was substituted by metals of the same period, like manganese [1][2][3][4][31][32][33][34][35]. The direct communication with electrodes was achieved at ITO and glassy carbon modified with a film of ddab, whenever the potentials for the redox transformations depend on the electrode surface.…”

Section: Discussionmentioning

confidence: 99%

“…In order to elucidate the role of the central metal atom in the formation of the different redox states of heme proteins during the catalytic cycle, different metals were inserted in the porphyrin [1][2][3]. For example, it has been shown that manganese substituted horseradish peroxidase (MnHRP) forms with H 2 O 2 an intermediate peroxo compound, which reacts slowly with reducing agents like ferrocytochrome c, ferrocyanide and ascorbic acid [2,3].…”

Section: Introductionmentioning

confidence: 99%