Properties and localization of the homoglutathione synthetase from Phaseolus coccineus leaves |
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Authors: | S Klapheck H Zopes H-G Levels L Bergmann |
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Institution: | Botanisches Inst der Univ. zu Köln, Gyrhofstrasse 15, D-5000 Köln 41, FRG. |
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Abstract: | The synthesis of homoglutathione (hGSH) by several plants of the tribe Phaseoleae is shown to be catalysed by a β-alanine-specific hGSH synthetase, Properties of the enzyme from Phaseolus coccineus L. cv. Preisgewinner were studied, using ammonium sulfate precipitates of primary leaf extracts. The hGSH synthetase showed a broad pH optimum at pH 8–9, an absolute requirement for Mg2+, a stimulation by K+, and a high affinity for γ-glutamylcysteine Km(app.) 73 μ M ]. The enzyme exhibited a high specificity for β-alanine Km(app.) 1.34 m M ] compared to glycine Km(app.) 98 m M ]. Chloroplasts, isolated from the leaves of Phaseolus coccineus , contained about 17% of the hGSH synthetase activity in the leaf cells. |
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Keywords: | Glutathione glutathione synthetase homoglutathione Phascolus coccineus |
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