Tülin AYDEMİR, Demet KAVRAYAN, Seda ÇINAR

Isolation and characterisation of polyphenoloxidase from Jerusalem artichoke (Helianthus tuberosus)

Polifenol oksidaz (PPO) enzimi yer elmasından izole edilmiştir. PPO, katekol, L-dopa, DL-dopa ya karşı aktivite göstermiş fakat bir monofenol olan L-tirozine karşı aktivite göstermemiştir. Yer elmasından izole edilen PPO nun optimum pH ve sıcaklık değeri sırasıyla 7.0 ve 25 °C dir. Enzim nötr pH civarında oldukça kararlıdır. 60 ve 80 °C deki aktivitenin % 50 inaktivasyonu için gerekli olan zaman sırasıyla, 40 ve 20 dakika olarak bulunmuştur. Katekol için Km ve Vmax değerleri sırasıyla, 5.88 mM ve 25 402 IU/mg.min dir. En çok inhibitör etkisi gösteren maddeler potasyum siyanid, β-merkaptoetanol ve tiyoüredir.

Anahtar Kelimeler:

izolasyon, katekol oksidaz, kararlılık, inhibitör, Helianthus tuberosus, yerelması, enzim aktivitesi

Polyphenol oxidase (PPO) was isolated from Jerusalem artichoke (Helianthus tuberosus). PPO showed activity to catechol, L-dopa and DL-dopa, but the enzyme had no activity toward L-tyrosine. PH and temperature optima Jerusalem artichoke PPO were 7,0 and 25 °C. The enzyme was significantly stable at neutral pH region. The times required for 50 % inactivation of activity at 60 and 80 °C were found to be 40 and 20 min. respectively. Km and Vmax values were 5.88 mM and 25 402 IU/mg.min with catechol, respectively. Most effective inhibitors was found to be thiourea β-mercaptoethanol and potassium cyanide.

Keywords:

isolation, catechol oxidase, stability, inhibitors, Helianthus tuberosus, Jerusalem artichokes, enzyme activity,

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