Properties and localization of the homoglutathione synthetase from Phaseolus coccineus leaves
1988; Wiley; Volume: 74; Issue: 4 Linguagem: Inglês
10.1111/j.1399-3054.1988.tb02045.x
ISSN1399-3054
AutoresS. Klapheck, Heinrich Zopes, H.‐G. Levels, L. Bergmann,
Tópico(s)Metabolism and Genetic Disorders
ResumoThe 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 Mg 2+ , a stimulation by K + , and a high affinity for γ‐glutamylcysteine [K m (app.) 73 μ M ]. The enzyme exhibited a high specificity for β‐alanine [K m (app.) 1.34 m M ] compared to glycine [K m (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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