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Regulation of violaxanthin de-epoxidase activity by pH and ascorbate concentration

In English

Författare

Summary, in English

The activity of violaxanthin de-epoxidase has been studied both in isolated thylakoids and after partial purification, as a function of pH and ascorbate concentration. We demonstrate that violaxanthin de-epoxidase has a Km for ascorbate that is strongly dependent on pH, with values of 10, 2.5, 1.0 and 0.3 mM at pH 6.0, 5.5, 5.0 and 4.5, respectively. These values can be expressed as a single Km±0.1±0.02 mM for the acid form of ascorbate. Release of the protein from the thylakoids by sonication was also found to be strongly pH dependent with a cooperativity of 4 with respect to protons and with an inflexion point at pH 6.7. These results can explain some of the discrepancies reported in the literature and provide a more consistent view of zeaxanthin formation in vivo.

Publiceringsår

1995

Språk

Engelska

Sidor

169-175

Publikation/Tidskrift/Serie

Photosynthesis Research

Volym

45

Issue

2

Dokumenttyp

Artikel i tidskrift

Förlag

Springer

Ämne

  • Biological Sciences

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 0166-8595