Pectic polysaccharides during ripening of mango (Mangifera indica L)

Abstract

The content of pectin decreased from 2.0 to 0.7% fresh weight (FW) and there was a concomitant increase in free galacturonic acid from 36 to 168 mg% FW during ripening of mango. Ion exchange chromatography on DEAE/cellulose resolved the pectic fraction into seven distinct peaks, with all of them showing a drastic decrease in pectin content and molecular weight as fruit ripening progressed, which indicated significant depolymerisation in vivo. Fraction I appeared to be an arabinogalactan-type polymer, while fractions II and III were heterogalacturonans containing more than 60% galacturonic acid. Hydrolases implicated in pectin depolymerisation were polygalacturonase (PG), pectin methyl esterase (PME), galactanase, arabinanase and β-galactosidase. They all showed a climacteric peak in activity during ripening, except for PME which showed a continuous decrease in activity after an initial increase. These results are discussed in the light of fruit softening during ripening.

Mango

“…There is a rapid increase in water soluble pectin (WSP), chelator-soluble polyuronides, chelator soluble carbohydrates and a decrease in total polyuronides in mango during ripening (Ali et al 2004;Chaurasia et al 2006). The cell wall hydrolases implicated in pectin depolymerization in mango are polygalacturonases (PG), pectinesterases (PE), β-1,4-glucanases, β-galactosidases, galactanases, arabinanases and pectin lyases (PL) (Abu-Sarra & Abu-Goukh 1992; Ali et al 1995;Ashraf et al 1981;Chaurasia et al 2006;Mitcham & McDonald 1992;Prasanna et al 2003Prasanna et al , 2005Roe & Bruemmer 1981). PG can exist in two forms either as exo-PG or endo-PG.…”

“…PG can exist in two forms either as exo-PG or endo-PG. In mango, mainly exo-PG seems to act and the activity of exo-PG increases as the fruit ripening proceeds (Abu-Sarra & Abu-Goukh 1992; Ali et al 2004;Mitcham & McDonald 1992;Prasanna et al 2003;Roe & Bruemmer 1981). The differential rate of fruit softening in mango is mainly due to the higher PG activity in the inner mesocarp than the outer tissue (Mitcham & McDonald 1992).…”

“…However, there are some contradictory reports which suggested weak correlation between PG activity and fruit softening (Abu-Sarra & Abu-Goukh 1992; Lazan et al 1986). Pectin esterases (PE) activity shows either a declining or constant trend during ripening (Ali et al 2004;Ashraf et al 1981;El-Zoghbi 1994;Prasanna et al 2003;Roe & Bruemmer 1981). Contrarily, an increase in PE activity during ripening of African mango 'Irvingiagabonensis' has also been reported (Aina & Oladunjoye 1993).…”

“…Cellulases also show enhanced activities during ripening (Abu-Sarra & Abu-Goukh 1992;El-Zoghbi 1994;Lazan et al 1986;Prasanna et al 2003;Roe & Bruemmer 1981). The role of other hydrolases such as β-galactosidases, galactanases, arabinanases (Ali et al 2004;Lazan & Ali 1993;Prasanna et al 2003Prasanna et al , 2005 in mango fruit softening has also been observed. The activity of β-galactosidase increases seven fold during ripening of mango (Ali et al 2004).…”

Multiple forms of β‐galactosidase from mango (Mangifera indica L Alphonso) fruit pulp

“…5 β-Galactosidase is also implicated in pectin dissolution by way of deglycosylating the β-galactan side chains which are generally present in pectintype polymers. 6 Mango being the most commercially important fruit of India, in the present study on Alphonso mango variety, β-galactosidase was isolated, purified and partially characterized. In addition, the presumed endogenous substrates of pectic-type polysaccharide were identified.…”