Free amino acids, with special study of 4-aminobutyrate, in succulent plants

Abstract

The cormatographic study of the free amino acids existing in Opuntia vulgaris (stem and fruit), Cereus tortuosus, Crassula portulacea and Sedum pachiphyllum has been carried out. We present the results obtained in the prospective work of glutamate decarboxylating enzyme in 23 plant species belonging to 6 botanical families of succulent plants. Glutamate decarboxylase is found in all the species Cactaceae, Euforbiaceae, Liliaceae, and Amaryllidaceae tested, not found, however, in the species of Crasulaceas and Aizoaceas that have been studied. The optimal pH (5.7-6.0) and the kinetic constant of Michaelis-Menten (1.6 and 4.7 x 10 ^ -3 M for Cereus tortuosus and Opuntia vulgaris respectively) coincide satisfactorily with the data published for this enzyme in plant origins. The apoenzymatic protein retains strongly bound, under the experimental conditions, to the coenzyme molecule (pyridoxal-5-phosphate). By salt fractionation, it has been possible to purify about twenty times the glutamate decarboxylase from Opuntia vulgaris (stem). Aminotransferic activities have been investigated in Opuntia vulgaris (stem and fruit). Cereus tortuosus (stem) and American Agave (flowers, leaves and escapes). In all these materials transaminating activity has been found between 4-aminobutyrate and 2-oxoglutarate, not finding appreciable activity when pyruvate and oxacetate are used as alpha-cet