The quantity of alcohol produced through wort fermentation is fundamental to a malt’s quality. Good fermentability is dependent on many malt quality parameters but requirement for proteases to provide amino acids and peptides for yeast is poorly understood. The thesis investigated relationships between amino acid profiles, endoprotease activities and fermentability under different malting and brewing conditions. Methods for measuring individual wort amino acids, endoprotease activity and fermentability were modified or developed to better understand the relationships. Levels of lysine and glycine were affected the most by malting and the variability was not always well predicted by the standard FAN analysis. Cysteine endoprotease activity developed similarly to total amino acids levels but associations were not significant Amino acids were limiting to fermentability at low yeast pitching rates and with the use of high maltose syrups but malt modification was the key determinant of fermentability. Studies on non fermentable sugar content were recommended.

The quantity of alcohol produced through wort fermentation is fundamental to a malt’s quality. Good fermentability is dependent on many malt quality parameters but requirement for proteases to provide amino acids and peptides for yeast is poorly understood. The thesis investigated relationships between amino acid profiles, endoprotease activities and fermentability under different malting and brewing conditions. Methods for measuring individual wort amino acids, endoprotease activity and fermentability were modified or developed to better understand the relationships. Levels of lysine and glycine were affected the most by malting and the variability was not always well predicted by the standard FAN analysis. Cysteine endoprotease activity developed similarly to total amino acids levels but associations were not significant Amino acids were limiting to fermentability at low yeast pitching rates and with the use of high maltose syrups but malt modification was the key determinant of fermentability. Studies on non fermentable sugar content were recommended.

No / Prohormone convertases (PCs) are endoproteases that process many substrates in addition to hormone precursors. Although overexpression of PCs is linked to carcinogenesis in some solid tumors, the role of subtilisin-kexin isoenzyme-1 (SKI-1) in this context is unknown. We show that SKI-1 is constitutively expressed in human pigment cells with higher SKI activity in seven out of eight melanoma cell lines compared with normal melanocytes. SKI-1 immunoreactivity is also detectable in tumor cells of melanoma metastases. Moreover, tissue samples of the latter display higher SKI-1 mRNA levels and activity than normal skin. From various stimuli tested, 12-O-tetradecanoylphorbol-13-acetate and tunicamycin affected SKI-1 expression. Importantly, SKI-1 inhibition by the cell-permeable enzyme inhibitor decanoyl-RRLL-chloromethylketone (dec-RRLL-CMK) not only suppressed proliferation and metabolic activity of melanoma cells in vitro but also reduced tumor growth of melanoma cells injected intracutaneously into immunodeficient mice. Mechanistic studies revealed that dec-RRLL-CMK induces classical apoptosis of melanoma cells in vitro and affects expression of several SKI-1 target genes including activating transcription factor 6 (ATF6). However, ATF6 gene silencing does not result in apoptosis of melanoma cells, suggesting that dec-RRLL-CMK induces cell death in an ATF6-independent manner. Our findings encourage further studies on SKI-1 as a potential target for melanoma therapy.