PURIFICATION AND MOLECULAR ANALYSIS OF AN EXTRACELLULAR GAMMA-GLUTAMYL HYDROLASE PRESENT IN YOUNG TISSUES OF THE SOYBEAN PLANT

A polypeptide present in intercellular wash fluids of young leaves of Glycine max has been purified to electrophoretic homogeneity. The prot ein has been identified as gamma-glutamyl hydrolase (GGH) based on the shared homology with a recently cloned cDNA from rat. The enzyme is p resent within the extracellular space of young leaves and a portion is bound to the cell wall. Northern and Western analysis confirm that th is polypeptide is expressed only in young (1-15 d old) leaf, stem and root tissue and is therefore expressed under a strict developmental pr ogram. The primary sequence of gamma-glutamyl hydrolase shares amino a cid identity with a cDNA clone from rat and two partially sequenced cD NAs from Arabidopsis. Although the complete in vivo function of gamma- glutamyl hydrolase in plants is unclear, it is known that the protein plays a critical role in folate metabolism and therefore likely in mee ting the physiological demands of growing plant tissues. (C) 1996 Acad emic Press, Inc.