Purification and characterisation of multiple forms of polygalacturonase from mango (Mangifera indica cv. Dashehari) fruit

Three multiple forms of polygalacturonase (PG) namely PGI, PGII and PGIII were isolated, purified and characterized from ripe mango (Mangifera indica cv. Dashehari) fruit. Native molecular weights of PGI, PGII and PGIII were found to be 120, 105 and 65 kDa, respectively. On SDS–PAGE analysis, PGI was found to be a homodimer of subunit size 60 kDa each while those of PGII and PGIII were found to be heterodimers of 70, 35 and 38, 27 kDa subunit size each, respectively. Three isoforms of PG differed with respect to the effect of pH, metals, reducing agents and their susceptibility towards heat. PG isoforms also differed with respect to the effect of substrate concentration on enzyme activity. PGI and PGIII exhibited inhibition at high substrate concentration while PGII did not. Km for polygalacturonic acid was found to be 0.02% for PGI.