Inhibitors of protein glycosylation or secretion change the pattern of extracellular proteins in suspension-cultured cells of Arabidopsis thaliana.

Cell walls are essential for plant development and morphogenesis. The majority of wall proteins are glycosylated, either as N- or O-glycans. Various inhibitors of glycosylation and secretion are used to determine the importance of wall proteins for the functioning of the walls. Tunicamycin is an inhibitor of the first enzyme in the N-glycosylation pathway, 3,4-dehydroproline inhibits peptidyl proline hydroxylation, and Brefeldin A is an inhibitor of vesicle trafficking, disrupting the delivery of wall polymers to the apoplast. In inhibitor-treated suspension-cultured Arabidopsis thaliana cells, qualitative and quantitative differences in the extracellular proteome were observed for both proteins secreted into medium or ionically-bound in the walls. Lack of O-glycosylation resulted in the selective protein loss from the extracellular compartments. Following tunicamycin treatment the secretion of additional proteins as well as ER-resident chaperones from the Hsp70 and Hsp90 families outside the protoplasts was noted. Moreover, changes in the proteolytic degradation pattern of culture filtrate proteins were also observed. Application of Brefeldin A resulted in transient and selective loss of individual proteins from the extracellular compartments of A. thaliana cell suspension. We conclude that post-translational modifications are vital for the proper functioning of wall proteins. N-glycosylation is crucial for their proper folding and stability. Extracellular compartments could also serve as a sink for improperly folded proteins during the unfolded protein response.

The elimination of meat from the diet selectively decreases pancreatic elastase secretion.

Since the vegetarian diet lacks the substrate for pancreatic elastase-1 as an enzyme, a decreased secretion of this enzyme could be expected. We aimed therefore to assess the changes of exocrine pancreatic secretion in a prospective way in a group of healthy omnivores who modified their diet by abstaining from meat for 1 month. Twenty healthy omnivores (fourteen females and six males) were used in the study. The nutrient intake was assessed for 7 d before commencing the study (omnivore diet) and after 1 month of dietary modification (modified diet; meat excluded). Similarly, the faecal output of pancreatic enzymes (elastase-1, chymotrypsin and lipase) was assessed before and 1 month after the period of dietary modification. Statistical differences between two points of the assessment (paired data) were calculated with the use of the Wilcoxon rank test. The relationship between the changes of faecal enzyme output and the changes in nutrient intake was assessed using multiple regression analysis. The dietary changes resulted in statistically significant decrease of faecal elastase-1 output (P < 0.05), whereas for chymotrypsin and lipase no changes were observed. No significant change in stool weight was recorded. No statistically significant correlation between changes in energy and nutrient consumption and changes in faecal output of pancreatic enzymes has been found. It was concluded that the exclusion of meat from the diet for a 1-month period results in significant changes in pancreatic secretion with a selective decrease of elastase-1 output. However, the underlying factor remains unclear.