Cysteine synthase from Capsicum annuum chromoplasts. Characterization and cDNA cloning of an up-regulated enzyme during fruit development
Cysteine synthase (O-acetylserine sulfhydrylase) has been purified to homogeneity from bell pepper (Capsicum annuum) fruit chromoplasts. This enzyme consists of two subunits of 35 kDa. Immunocytochemical localization experiments confirmed the plastid location of this enzyme. A full-length cDNA was i...
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Veröffentlicht in: | The Journal of biological chemistry 1992-09, Vol.267 (25), p.17966-17970 |
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Zusammenfassung: | Cysteine synthase (O-acetylserine sulfhydrylase) has been purified to homogeneity from bell pepper (Capsicum annuum) fruit
chromoplasts. This enzyme consists of two subunits of 35 kDa. Immunocytochemical localization experiments confirmed the plastid
location of this enzyme. A full-length cDNA was isolated from an expression library of C. annuum. The deduced peptide sequence
revealed high similarity between the C. annuum cysteine synthase and its bacterial counterparts. In vitro transcription and
translation of the cDNA and subsequent import experiments demonstrated that the encoded cysteine synthase is located in the
plastids. The steady-state level of the cysteine synthase mRNA is almost constant in dark-grown hypocotyls, leaves, and fruits.
However, a slight increase in this mRNA level was detected during fruit development (when the 25 S rRNA was taken as an internal
standard). Similarly, the cysteine synthase activity in plastids was found to increase during fruit development and reaches
the highest levels in the chromoplasts of red fruits. To address the physiological role of this phenomenon, we have shown
that cysteine is engaged in the active metabolism of glutathione. Thus, in connection with the previous demonstration of an
active tocopherol metabolism, it is concluded that differentiation of chloroplast to chromoplast in C. annuum involves an
active synthesis of potential antioxidants or redox modulators. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1016/S0021-9258(19)37137-6 |