Proteólise em sementes de Angico (Anadenanthera colubrina) na germinação

Abstract

Protein reserves hydrolysis is a central process of germination. Coordinated by different peptidases that act sequentially and overlaid mode, this proteolytic process provides a steady supply of amino acids to the full development of the embryo into seedling. These enzymes are an ancient group of proteins that have evolved separately in a wide structural and functional diversity. They virtually participate in all cellular processes of living beings and have wide applications in medicine, pharmacy and industry. However, the explanatory models of the germination proteolytic mechanisms were obtained from studies almost restricted to a few plant species, cultivated for a long time, under constant genetic improvement. This narrow genetic basis imply caution about generalizations made from these models, as well restricts the biological knowledge about the plant kingdom and the technological use of plant peptidases. In this work, a scan of the proteolytic activity was held in germinating seeds of a leguminous woody tree – Angico (Anadenanthera colubrina). By using spectrofluorometry and high pression liquid chromatography, combined with fluorescent peptide substrates and peptidase inhibitors, at least nine peptidase activities related to the classes of aspartyl-, cysteine-, serine- and metallo-peptidases were detected and quantified in crude protein extracts of the embryonic axis and the cotyledons excised before, during and after germination. The occurrence and intensity of these activities varied over time and between these tissues. Among the activities detected, there was indication that aspartyl-endopeptidases (phytopepsins) and cysteinecarboxypeptidases (plant cathepsins-B) are involved in the hydrolysis of A. colubrina protein reserves, which differ from the peptidases involved in commonly cultivated legumes. In addition, one of the phytopepsins detected showed stability on the pH scale, which is important for industrial uses. These peptidases must be isolated so that structural and functional studies could confirm these indications. However, with the data obtained from Angico, the biological and technological importance of extending the studies on plant peptidases on a diverse genetic basis is evident. In this regard, the methodology used allowed a wide detection of peptidases on independent sets of samples, which would allows, for example, comparisons between different species.