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RATE‐LIMITING ENZYMES IN THE LIBERATION OF AMINO ACIDS IN MASHING
Author(s) -
Sopanen T.,
Takkinen P.,
Mikola J.,
Enari T.M.
Publication year - 1980
Publication title -
journal of the institute of brewing
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.523
H-Index - 51
eISSN - 2050-0416
pISSN - 0046-9750
DOI - 10.1002/j.2050-0416.1980.tb06868.x
Subject(s) - mashing , carboxypeptidase , liberation , chemistry , amino acid , enzyme , biochemistry , limiting , mechanical engineering , engineering , in vitro
When 29 malts representing a wide variation in free amino nitrogen of wort were mashed for 3 h at 45°C, the increases in TCA‐soluble amino nitrogen varied from 47 to 116 μmoles per gramme of malt. The carboxypeptidase activities of the malts showed only small positive correlations with the increase of amino nitrogen during mashing. Inactivation of the different malt carboxypeptidases by 70 to 90% with diisopropylfluorophosphate decreased the liberation of amino nitrogen by only 5 to 25%. Moreover, addition of purified malt carboxypeptidase I to the mashing suspensions had no effect on the liberation of amino nitrogen. It is therefore evident that the carboxypeptidases do not have a major rate‐limiting role in the liberation of amino acids in mashing, although it has earlier been shown that they are essential enzymes in this process. The proteinase activities of the malts, determined using two methods, correlated strongly with the liberation of amino nitrogen in mashing. Addition of crude malt proteinase to the mash increased, and addition of purified barley proteinase inhibitor decreased the measured proteinase activity and the liberation of amino acids roughly to the same extent. These results indicate that the most important rate‐limiting enzyme activity in the liberation of amino acids in mashing is the proteinase activity of the malt.