Evaluation of the presence of aspartic proteases from Centaurea calcitrapa during seed germination

Investigation of plant latices of Asteraceae and Campanulaceae regarding proteolytic activity

Occurrence of plant latices is widespread, there are more than 40 families of plants characterized to establish lactiferous structures. The appearance of hydrolytic active proteins, incorporated in latices is already characterized, and hydrolytic active proteins are considerable, and for several plant families, the occurrence of hydrolytic active proteins is already specified e.g. Apocynaceae Juss., Caricaceae Dumort, Euphorbiaceae Juss., Moraceae Gaudich and Papaveraceae Juss. In our investigation, focused on latex bearing plants of order Asterales, Asteraceae and Campanulaceae in particular. The present outcomes represent a comprehensive study, relating to the occurrence of proteolytic active enzymes of order Asterales for the first time. 131 different species of Asteraceae and Campanulaceae were tested, and the appearance of plant latex proteases were determined in different quantities. Proteolytic activity was investigated by inhibitory studies and determination of residual activity in the following, enable us to characterize the proteases. Most of the considered species exhibit a serine protease activity and a multiplicity of species exhibited two or more subclasses of proteases.

Proteolysis of the peanut allergen Ara h 1 by an endogenous aspartic protease

The 7S and 11S globulins of peanuts are subjected to proteolysis two days after seed imbibition, with Ara h 1 and the arachin acidic chains being among the first storage proteins to be mobilized. Proteolytic activity was greatest at pH 2.6-3 and is inhibited by pepstatin A, characteristic of an aspartic protease. This activity persists in seedling cotyledons up to at least 8 days after imbibition. In vitro proteolysis of Ara h 1 at pH 2.6 by extracts of cotyledons from seedlings harvested 24 h after seed imbibition generates newly appearing bands on SDS-PAGE. Partial sequences of Ara h 1 that were obtained through LC-MS/MS analysis of in-gel trypsin digests of those bands, combined with information on fragment size, suggest that proteolysis begins in the region that links the two cupin domains to produce two 33/34 kD fragments, each one encompassing an intact cupin domain. The later appearance of two 18 and 10/11 kD fragments can be explained by proteolysis within an exposed site in the cupin domains of each of the 33/34 kD fragments. The same or similar proteolytic activity was observed in developing seeds, but Ara h 1 remains intact through seed maturation. This is partly explained by the observation that acidification of the protein storage vacuoles, demonstrated by vacuolar accumulation of acridine orange that was dissipated by a membrane-permeable base, occurs only after germination. These findings suggest a method for use of the seed aspartic protease in reducing peanut allergy due to Ara h 1.

Differential elicitation of an aspartic protease inhibitor: regulation of endogenous protease and initial events in germination in seeds of Vigna radiata

Plant aspartic proteases are of recent origin with their physiological significance in crucial processes emerging. Reports on the significance of aspartic protease inhibitors and their endogenous proteases in seeds of plants are scanty. This paper reports the purification of an aspartic protease inhibitor from the seeds of Vigna radiata, its control of the endogenous aspartic protease and their subsequent role in the early germination events. The role of the aspartic protease inhibitor and the enzyme in initial stages of germination of V. radiata has been tracked by differential timed expression and germination assays. The expression pattern revealed maximum expression of the inhibitor in the dormant seeds while the enzyme was predominant in the germinating seeds. Their expression patterns and interactions indicate their significance in initiation of germination. The expression of other classes of proteases was monitored during germination and a model predicting the events occurring during proteolysis of the storage protein in germination is hypothesized. The inhibitor was a linear, hydrophobic, pH stable and thermostable peptide with molecular weight of 1660 Da. The purified inhibitor showed a pI of 4.36 with the sequence as AEIYN KDGNK LDLYG. The inhibitor was found to be stable in a broad range of pH from 2 to 10 with an optimum of 3.0. The half-life of VrAPI at 100 degrees C was 30 min whereas the maximum activity was observed at 37 degrees C. The initial kinetic analysis of the inhibitor against the endogenous protease showed an IC(50) value of 11 nM while the value of the inhibition rate constant K(i) was 34 x 10(-9)M.