Abstract

ENEAS-FILHO, JOAQUIM et al. Isolation  and partial purification of b-galactosidases from cotyledons of two cowpea cultivars. Rev. Bras. Fisiol. Veg. [online]. 2001, vol.13, n.3, pp. 251-261. ISSN 0103-3131.  http://dx.doi.org/10.1590/S0103-31312001000300001.

Three isoforms of b-galactosidases were isolated and partially purified from the cotyledons of quiescent seeds of Vita 3 and Vita 5 cowpea [Vigna unguiculata (L.) Walp.] cultivars differing in water and salt stress tolerance. The purification procedure consisted of ammonium sulfate fractionation, acid precipitation, ion exchange chromatography through DEAE-sephadex and affinity chromatography through Lactosyl-sepharose columns. The three isoforms isolated from the two cultivars showed the same chromatographic patterns, same optimum of temperature for enzyme activity assay (60ºC),  identical  thermal stability up to 50°C,  and  similar  pH  optima (3-4). However, they differed from each other in sensitivity towards metal ions and certain chemical agents presents in the assay medium.  The results have shown that the observed differences in b-galactosidases from the cotyledons of quiescent seeds were not sufficient to relate them to stress tolerance.

Keywords : cotyledons; isozymes; Vigna unguiculata; Vita 3 and Vita 5 cultivars; salt tolerance.