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. 1973 Apr;51(4):755–759. doi: 10.1104/pp.51.4.755

The Presence of Ribulose 1,5-Diphosphate Carboxylase in the Nonphotosynthetic Endosperm of Germinating Castor Beans 1

C R Benedict a
PMCID: PMC366340  PMID: 16658404

Abstract

Ribulose 1,5-diphosphate carboxylase was detected in extracts of germinating castor bean (Ricinus communis var. Hale) endosperms. This is the first report of this enzyme in a nonphotosynthetic (no chlorophyll) plant tissue. Radioactive 3-phosphoglyceric acid has been identified as the principle product resulting from the enzymatic condensation of 14C-bicarbonate and ribulose-1,5-diP in endosperm extracts. The Km values of bicarbonate and ribulose-1,5-diP for the endosperm carboxylase are 1.14 × 10−2m and 7.5 × 10−5m, respectively. The carboxylase activity peaks at 4 days in endosperms of castor beans germinated in the dark. The specific activity of the carboxylase at this stage of germination is 4.3 μmoles of 3-phosphoglycerate formed/mg protein·hr. The presence of ribulose-1,5-diP carboxylase and other enzymes of the reductive pentose phosphate pathway show the potential of this pathway in castor bean endosperms.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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