Biochemical and molecular characterization of [alpha]-D-galactosidase from coffee beans

[alpha]-D-Galactosidase ([alpha]-Gal; EC 3.2.1.22) is one of three principal enzymes involved in the modification or degradation of plant cell wall galactomannans. In the present paper it is shown that [alpha]-galactosidase activities in field-grown coffee beans are variable amongst cultivars of the two species investigated (Coffea arabica and C. canephora var. Robusta). Higher activities were found in Arabica cultivars. Using beans from greenhouse-cultivated C. arabica as a model, we showed that [alpha]-Gal activity was undetectable in the bean perispem tissue, but increased gradually during the endosperm development, to reach a peak at approximately 30 weeks after flowering (WAF) which coincided with the hardening of the endosperm. [alpha]-Gal-specific transcripts detected at 22 and 27 WAF accompanied the peak of [alpha]-Gal activity, but were reduced to be undetectable in mature beans at 30 WAF, while [alpha]-Gal activity still persisted. Two isoforms were distinguished in 2-DE profiles of crude protein extracts by N-terminal sequencing analysis. Analysis of two-dimensional gel electrophoresis profiles demonstrated that both isoforms accumulated in a linear fashion throughout grain maturation. [alpha]-Gal activity was also observed to increase to high levels during in vitro germination of coffee beans suggesting an important function of this enzyme in this process. [alpha]-Gal cDNA sequences from Arabica and Robusta were sequenced and their deduced proteins appeared to be very similar, differing by only eight amino acids. Southern-blot analysis suggests that the enzyme was encoded by at least two genes in C. arabica that could explain the existence of the two isoforms identified in 2-DE profiles.

Bibliographic Details

Main Authors:	Marraccini, Pierre, Rogers, William John, Caillet, Victoria, Deshayes, Alain, Granato, Dominique, Lausanne, Françoise, Lechat, Sylvianne, Pridmore, David, Pétiard, Vincent
Format:	article biblioteca
Language:	eng
Published:	Elsevier
Subjects:	F60 - Physiologie et biochimie végétale, F30 - Génétique et amélioration des plantes, Coffea arabica, Coffea canephora, alpha galactosidase, mannane, paroi cellulaire, fève de café, développement biologique, germination, activité enzymatique, variété, http://aims.fao.org/aos/agrovoc/c_1721, http://aims.fao.org/aos/agrovoc/c_1723, http://aims.fao.org/aos/agrovoc/c_29488, http://aims.fao.org/aos/agrovoc/c_4587, http://aims.fao.org/aos/agrovoc/c_1415, http://aims.fao.org/aos/agrovoc/c_28379, http://aims.fao.org/aos/agrovoc/c_921, http://aims.fao.org/aos/agrovoc/c_3247, http://aims.fao.org/aos/agrovoc/c_2604, http://aims.fao.org/aos/agrovoc/c_8157,
Online Access:	http://agritrop.cirad.fr/530027/ http://agritrop.cirad.fr/530027/1/document_530027.pdf
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