Isolation and characterization of invertase inhibitor from sweet potato storage roots

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Title:	Isolation and characterization of invertase inhibitor from sweet potato storage roots
Authors:	黃冠中(Huang Guan-jhong);許明志(Ming-Jyh Sheu);張永勳(Yuan Shiun Chang);陸德齡(Lu Te-Ling);(Heng-Yuan Chang);(Shyh-Shyun Huang);(Yaw-Huei Lin)*
Contributors:	藥學院中國藥學研究所
Keywords:	sweet potato;invertase inhibitor;gene expression;recombinant protein
Date:	2008-12
Issue Date:	2009-08-19 17:24:39 (UTC+8)
Abstract:	BACKGROUND: Plant invertases play important roles in sucrose metabolism. Cell wall invertase has been reported to participate in phloem loading and unloading. Soluble invertases are involved in hexose level regulation in mature tissues and in utilisation of stored sucrose within vacuoles. Invertase inhibitory proteins have been described as one of the possible components for invertase activity regulation in some plant species. RESULTS: In this work an invertase inhibitor (ITI) coding sequence was cloned by differential display from sweet potato (SP) storage roots. SPITI codes for a protein of 192 amino acids with a predicted molecular mass of 20 624 Da containing a 20-amino-acid signal peptide and four cysteines. Computer analysis of the deduced amino acid sequences of the conserved domain revealed that the protein belonged to the plant invertase/pectin methylesterase inhibitor. Both the corresponding mRNA and protein levels were found to be highest in storage roots, followed by veins. Recombinant SPITI protein from the storage root cDNA clone overproduced in Escherichia coli (M15) was purified by affinity chromatography. This protein effectively inhibited the invertase activity in a dose-dependent manner. The results presented in the Lineweaver-Burk plots indicated that the invertase inhibitor displayed a mode of competitive inhibition towards the invertase tested, with a Ki of 3.82 × 10−6 mol L−1. CONCLUSION: These results suggested that SPITI is a novel member of the ITI family in plants. SPITI genes of sweet potato storage roots display differential gene expression patterns, which may be associated with sucrose metabolism to cope with particular developmental requirements. Copyright © 2008 Society of Chemical Industry
Relation:	JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 88(15):pp2615~2621
Appears in Collections:	[Graduate Institute of Chinese Pharmaceutical Science] Journal articles

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