Walter, Mary Winifred (1963)
Biosynthesis of galactosylsucrose derivatives.
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The biosynthesis of the "raffinose family" of oligosaccharides in Vicia faba seeds has been investigated in vitro. Preliminary experiments have shown that the oligosaccharides are synthesised as the seeds mature and reach a maximum concentration at the dormant stage. Raffinose (the lowest member of the series), has been synthesized via two routes: UTP Uridine triphosphate ATP Adenosine triphosphate UDP Uridine diphosphate UDP-Glucose Uridinediphospho-D-glucose UDP-galactose Uridinediphospho-D-galctose. ADP-galactose Adenosinediphospho-D-galactose NAD Nicotinamide adenine dinucleotide. ADP-galactose was considered as a possible galactose donor, but attempts to synthesize this compound from ATP and a-D-galactose-1-phosphate were unsuccessful. The combined evidence strongly suggests that UDP-galactose is the galactose donor in (a), and that such a reaction could occur in vivo.V.faba (b) Melibiose + sucrose alpha-galactosidase raffinose + glucose In connection with this, the properties of V. faba a-galactosidase were examined. It was shown that the trisaccharide planteose was also formed in reaction (b), but in much smaller quantities than the isomeric raffinose. The biosynthesis of raffinose in vivo by either or both of these reactions is discussed.Stachyose has also been synthesized via a-galactosidase using raffinose as substrate. Again the possibility of this reaction occurring in vivo is discussed. Another enzyme found to occur in dormant V, faba seeds is alkaline B-fructofuranosidase. The properties of this enzyme were examined and compared with other B-fructo-furanosidases known to occur in plant tissues. The enzyme was shown to hydrolyse beta-D-fructofuranosides and to transfer a fructosyl residue to sucrose forming 1 F-beta-fructosylsucrose. The possibility of this enzyme and alpha-galactosidase being involved in the breakdown of raffinose oligosaccharides in vivo is considered.
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in Royal Holloway Research Online.Last modified on 01-Feb-2017
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Institution: University of London, Royal Holloway College (United Kingdom).