β-Galactosidase and its significance in ripening mango fruit

• Published in: Phytochemistry (Oxford) 1995-03, Vol.38 (5), p.1109-1114
• Main Authors: Ali, Zainon Mohd, Armugam, Santhi, Lazan, Hamid
• Format: Article
• Language: English
• Subjects: beta-Galactosidase - isolation & purification; beta-Galactosidase - physiology; Biological and medical sciences; Biotechnology; Chromatography, Gel; Chromatography, Ion Exchange; Fructification and ripening; Fruit - enzymology; Fruit - growth & development; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Isoenzymes - physiology; Plant physiology and development; Vegetative and sexual reproduction, floral biology, fructification
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/0031-9422(94)00804-3

The fruit extracts of ripening cv. Harumanis mango contained a number of glycosidases and glycanases. Among the glycosidases, β- d-galactosidase (EC 3.2.1.23) appeared to the most significant. The enzyme activity increased in parallel with increase in tissue softness during ripening. Mango β-galactosidase was fractionated into three isoforms, viz. β-galactosidase I, II and III by a combination of chromatographic procedures on DEAE-Sepharose CL-6B, CM-Sepharose and Sephacryl S-200 columns. Apparent K m values for the respective β-galactosidase isoforms for p-nitrophenyl β- d-galactoside were 3.7, 3.3 and 2.7 mM, and their V max values were 209, 1024 and 62 nkat mg −1 protein. Optimum activity occurred at ca pH 3.2 for β-galactosidase I and II, and pH 3.6 for β-galactosidase III. Mango β-galactosidase and its isoforms have galactanase activity, and the activity of the latter in the crude extracts generally increased during ripening. The close correlation between changes in β-galactosidase activity, tissue softness, and increased pectin solubility and degradation suggests that β-galactosidase might play an important role in cell wall pectin modification and softening of mango fruit during ripening.