Singh Poorinima, Dwivedi Upendra N
Department of Biochemistry, University of Lucknow, Lucknow, Uttar Pradesh 226 007, India.
Department of Biochemistry, University of Lucknow, Lucknow, Uttar Pradesh 226 007, India.
Food Chem. 2008 Nov 15;111(2):345-9. doi: 10.1016/j.foodchem.2008.03.072. Epub 2008 Apr 1.
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 65kDa, respectively. On SDS-PAGE analysis, PGI was found to be a homodimer of subunit size 60kDa each while those of PGII and PGIII were found to be heterodimers of 70, 35 and 38, 27kDa 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.
从成熟的芒果（芒果品种Dashehari）果实中分离、纯化并鉴定了三种多聚半乳糖醛酸酶（PG）的多种形式，即PGI、PGII和PGIII。发现PGI、PGII和PGIII的天然分子量分别为120、105和65kDa。SDS-PAGE分析表明，PGI是由两个大小均为60kDa的亚基组成的同型二聚体，而PGII和PGIII分别是由大小为70、35和38、27kDa的亚基组成的异型二聚体。三种PG同工型在pH值、金属、还原剂的影响以及它们对热的敏感性方面存在差异。PG同工型在底物浓度对酶活性的影响方面也存在差异。PGI和PGIII在高底物浓度下表现出抑制作用，而PGII则没有。PGI对聚半乳糖醛酸的Km值为0.02%。
