水稻籽粒（Oryza sativa）中转化酶同工酶的部分纯化及特性分析

Partial purification and characterization of invertase isozymes from rice grains (Oryza sativa).

作者信息

Charng Y Y, Juang R H, Su J C, Sung H Y

机构信息

Department of Agricultural Chemistry, National Taiwan University, Taipei, R.O.C.

出版信息

Biochem Mol Biol Int. 1994 Jun;33(3):607-15.

PMID:7951078

Abstract

Four invertase isozymes have been isolated from the milky stage rice grains. According to the pH optima, they are classified as one alkaline (IT7) and three acid invertases. The acid invertases are further divided into two soluble forms (IT4 and IT5) and one cell wall-bound (ITb) form which was solubilized in 1 M NaCl. The pH optima of ITb, IT4, IT5 and IT7 are 4.5, 3.5-4.0, 5.0 and 7.0, and the molecular masses are 42, 60, 64 and 260 kDa, respectively. Both IT4 and IT5 were bound to Con A-Sepharose suggesting that these enzymes are glycoprotein. The Km of ITb, IT4, IT5 and IT7 for sucrose are 4.3, 0.9, 12.1 and 70.1 mM, respectively. IT4 and IT5 have a higher Km for raffinose, and the maximum activities are 64% and 27% of that using sucrose as the substrate. IT7 did not hydrolyze raffinose at all. These invertases also exhibit distinct isoelectric points (pI) and different susceptibility to various inhibitors.

摘要

已从乳熟期水稻籽粒中分离出四种转化酶同工酶。根据最适pH值，它们被分类为一种碱性转化酶（IT7）和三种酸性转化酶。酸性转化酶进一步分为两种可溶性形式（IT4和IT5）和一种细胞壁结合形式（ITb），后者可在1 M NaCl中溶解。ITb、IT4、IT5和IT7的最适pH值分别为4.5、3.5 - 4.0、5.0和7.0，分子量分别为42、60、64和260 kDa。IT4和IT5均与伴刀豆球蛋白A - 琼脂糖结合，表明这些酶是糖蛋白。ITb、IT4、IT5和IT7对蔗糖的Km值分别为4.3、0.9、12.1和70.1 mM。IT4和IT5对棉子糖的Km值较高，其最大活性分别为以蔗糖为底物时的64%和27%。IT7根本不水解棉子糖。这些转化酶还表现出不同的等电点（pI）以及对各种抑制剂的不同敏感性。