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Enzyme Research
Volume 2010, Article ID 517283, 5 pages
http://dx.doi.org/10.4061/2010/517283
Research Article

Characterization of Activity of a Potential Food-Grade Leucine Aminopeptidase from Kiwifruit

School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand

Received 14 June 2010; Revised 25 August 2010; Accepted 4 October 2010

Academic Editor: Raffaele Porta

Copyright © 2010 A. A. A. Premarathne and David W. M. Leung. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Aminopeptidase (AP) activity in ripe but firm fruit of Actinidia deliciosa was characterized using L-leucine-p-nitroanilide as a substrate. The enzyme activity was the highest under alkaline conditions and was thermolabile. EDTA, 1,10-phenanthroline, iodoacetamide, and Z n 2 + had inhibitory effect while a low concentration of dithiothreitol (DTT) had stimulatory effect on kiwifruit AP activity. However, DTT was not essential for the enzyme activity. The results obtained indicated that the kiwifruit AP was a thiol-dependent metalloprotease. Its activity was the highest in the seeds, followed by the core and pericarp tissues of the fruit. The elution profile of the AP activity from a DEAE-cellulose column suggested that there were at least two AP isozymes in kiwifruit: one unadsorbed and one adsorbed fractions. It is concluded that useful food-grade aminopeptidases from kiwifruit could be revealed using more specific substrates.