Authors: Oranuch Leelapon Gautam Sarath Paul E Staswick
Publish Date: 2004/07/23
Volume: 219, Issue: 6, Pages: 1071-1079
Abstract
Soybean Glycine max L Merr contains two proteins called vegetative storage proteins VSPs that function as temporary storage reserves but are also closely related to plant acid phosphatases of the haloacid dehalogenase HAD superfamily This study examined the biochemical basis for the relatively low catalytic activity previously reported for these VSPs The specific activity of purified recombinant VSPα on GMP was about 40fold lower than for a related soybean root nodule acid phosphatase APase which had a specific activity of 845 U mg−1 protein Conversion of Ser106 to Asp increased VSPα activity about 20fold This Asp residue is present in nodule APase and is a highly conserved nucleophile in the HAD superfamily Related VSPs from cultivated soybean and from three wild perennial soybeans as well as a pod storage protein PSP from Phaseolus vulgaris L all lack the catalytic Asp suggesting they too are catalytically inefficient Phylogenetic analysis showed the VSPs and PSP are more closely related to each other than to 21 other VSPlike proteins from several plant species all of which have the nucleophilic Asp This study suggests that loss of catalytic activity may be a requirement for the VSPs and PSP to function as storage proteins in legumesWe thank Martha Rowe for her technical assistance in carrying out this study This is Journal Series Paper No 14443 A contribution of the University of Nebraska Agricultural Research Division Lincoln NE 68583 This work was supported in part by NIH Grant Number 1 P20 RR16469 from the BRIN Program of the National Center for Research Resources GS
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