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Dr Vesna Maksimovic
Laboratory for Plant Molecular Biology
Institute of Molecular Genetics and Genetic Engineering
Vojvode Stepe 444A, PO Box 446, Belgrade, Serbia & Montenegro
Email: heljda@sezampro.yu
Tel: 381 11 39 76 658
Fax: 381 11 75 808

We are interested in the analysis of potential biological function(s) of aspartic proteinases (AP) in buckwheat (Fagopyrum esculentum Moench). The heterodimeric 47 kDa form of AP has been purified by pepstatinA affinity chromatography from acidic protein extracts of buckwheat seeds and it was shown that this fraction cross-reacted with antibodies raised against barley phytepsin. Specific proteolytic activity of this protein fraction towards several substrates was confirmed in vitro. The analysis of time course expression revealed that the 47 kDa AP accumulated during seed maturation and was also present at the beginning of germination, suggesting possible involvement in seed storage protein maturation and degradation. From the cDNA library of developing buckwheat seeds we also isolated cDNA coding an aspartic-like proteinase with unknown biological function and still non-approved proteolytic activity. Analysis of its deduced amino acid sequence showed the presence of two active sites characteristic for plant aspartic proteinases (DTG-DSG), but absence of a PSI (Plant Specific Insert). Comparison of the deduced a.a. sequence characterized by the two domain structure, showed intriguing homology with candidapepsin precursor from Candida albicans, as well as with mammalian aspartic proteinases (chymosin precursor/ cathepsin E precursor /pepsinogen ). Homology was also noticed with nucleoid DNA-binding protein from Arabidopsis and human aspartyl protease-3 related to Altzheimer's disease.
Besides fundamental aspects, we have focused our attention on the potential biotechnological use of buckwheat in connection with the milk-clotting ability detected for the 47kDa aspartic proteinase from its seeds.
Gordana S. Timotijevi_ , Svetlana R. Radovi_, Vesna R. Maksimovi_,:
1. Characterization of an aspartic proteinase activity in buckwheat (Fagopyrum esculentum Moench) seeds, Journal of Agricultural and Food Chemistry 2003, 51, 2100-2104
2. Plant aspartic proteinases as a possible vegetable rennet: purification and properties of aspartic proteinase from buckwheat seed Submitted for publication in Journal of Agricultural and Food Chemistry, 2004

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