Articles
PARTIALLY PURIFICATION OF MG-DECHELATASE IN RELATION TO CHLOROPHYLL DEGRADATION IN BROCCOLI (BRASSICA OLERACEA L. ITALICA GROUP) FLORETS
Article number
875_66
Pages
509 – 514
Language
English
Abstract
Involvement of Mg-dechelatase in relation to chlorophyll (Chl) degradation of stored broccoli (Brassica oleracea L. Italica Group) florets was investigated to clarify the mechanism of Chl degradation.
Mg-dechelation activity in floret extracts was found in two different molecular weight fractions – a low molecular weight (<5,000) fraction (LMWF) and a high molecular weight (>5,000) fraction (HMWF), which seemed to be Mg-dechelatase, using chlorophyllin (Chlin) a or chlorophyllide (Chlide) a as a substrate.
Mg-dechelation activity of the extract from broccoli florets, which were stored for 4 days at 15°C, was higher than that of extracts from fresh broccoli florets using Chlin a or Chlide a as a substrate.
High molecular weight substance (HMWS), which has a Mg-dechelation activity, was purified by (NH4) 2SO4 precipitation (20-60% saturation), molecular exclusion chromatography (Sephacryl S-200), anionic exchange chromatography (DEAE-650M), hydrophobic interaction chromatography (Butyl-650M) and molecular exclusion chromatography (HW-55F). Only one peak of the activity was detected in fresh broccoli extract and no other isozyme with Mg-dechelating action was found in the yellow broccoli extract and molecular mass was about 70 KDa.
This high-molecular weight substance shows strong activity with artificial substrate, Chlin a, but hardly have an activity with native substrates, Chlide a. Moreover, low molecular weight substance from 5,000 to 10,000 also had a Mg-dechelation activity.
This means that HMWS does not have an activity with Chlide a. It is interpreted by the results obtained in this study that HMWS is not involved in Chl degradation of broccoli florets.
Mg-dechelation activity in floret extracts was found in two different molecular weight fractions – a low molecular weight (<5,000) fraction (LMWF) and a high molecular weight (>5,000) fraction (HMWF), which seemed to be Mg-dechelatase, using chlorophyllin (Chlin) a or chlorophyllide (Chlide) a as a substrate.
Mg-dechelation activity of the extract from broccoli florets, which were stored for 4 days at 15°C, was higher than that of extracts from fresh broccoli florets using Chlin a or Chlide a as a substrate.
High molecular weight substance (HMWS), which has a Mg-dechelation activity, was purified by (NH4) 2SO4 precipitation (20-60% saturation), molecular exclusion chromatography (Sephacryl S-200), anionic exchange chromatography (DEAE-650M), hydrophobic interaction chromatography (Butyl-650M) and molecular exclusion chromatography (HW-55F). Only one peak of the activity was detected in fresh broccoli extract and no other isozyme with Mg-dechelating action was found in the yellow broccoli extract and molecular mass was about 70 KDa.
This high-molecular weight substance shows strong activity with artificial substrate, Chlin a, but hardly have an activity with native substrates, Chlide a. Moreover, low molecular weight substance from 5,000 to 10,000 also had a Mg-dechelation activity.
This means that HMWS does not have an activity with Chlide a. It is interpreted by the results obtained in this study that HMWS is not involved in Chl degradation of broccoli florets.
Authors
S. Kaewsuksaeng, N. Yamauchi, Y. Funamoto, S. Aiamla-Or, M. Shigyo, S. Kanlayanarat
Keywords
chlorophyll degradation, Mg-dechelatase, heat treatment, broccoli (Brassica oleracea L. Italica Group)
Online Articles (73)