Chemical Control of Photorespiration: Steady-State Kinetic and Conformational Changes of Ribulose-L,5-Bisphosphate Carboxylase Oxygenase Obtained with O-P-Nitrophenylhydroxylamine

C. J. Van Assche, N. Reinier, B. Courtiade, A. Chancel, S. Huber

Research output: Contribution to journalArticle

Abstract

Spinach RuBP carboxylase-oxygenase (Rubisco) purified from the commercially available enzym e, underwent kinetic changes when micromolar concentrations of O-p-nitrophenylhydroxvlamine (NPHA) were applied on fully activated enzyme. Under steady-state conditions, a decrease of Km CO2 was observed without changes in Vmax. Double reciprocal plots showed a com petitive stimulation of carboxylase function. The substrate specificity factor k = Vc KJVQKc was increased from approximatively 15—20% upon treatment with NPHA, using both parallel and sim ultaneous determ inations of RuBP-carboxylase and oxygenase activities. Such a limitedchange in partition between Rubisco functions actually resulted into an in CO2 fixation of intact soybeans leaves treated with NPHA, arising from a substantial alleviation of O2-inhibition ofphotosynthesis. From spectrophotom etric and sulfhydryl group titration data, evidence was accumulated for a conformational change of the native enzyme, induced by NPHA, bringing about an increased ratio of carboxylase to oxygenase activities. Direct interaction of NPHA with a cysteine residue of Rubisco near the catalytic site, appears as a candidate for such chemically-induced conformational modification.

Original languageEnglish (US)
Pages (from-to)837-844
Number of pages8
JournalZeitschrift fur Naturforschung - Section C Journal of Biosciences
Volume42
Issue number7-8
DOIs
StatePublished - Aug 1 1987

Keywords

  • Chemical Stimulation
  • O-p-nitrophenylhydroxylamine
  • Photorespiration
  • Rubisco
  • Substrate- Specificity Factor

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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