Investigation on the Peptidases of Green Malt

Abstract

(1) One of the authors, M. SATO, had once carried out an investigation^(1)(2)(3)(4) on the peptidases of green malt, using green malt of Danish barley from the Danish Factories in Salgelse as well as Danish brewery malt from the Carlsberg Beer Breweries and synthesizing, as substrates, LG, LGG, LGGG, AG, and AGG, etc. In the present investigation, the authors carried out experiments on the peptidases, using green malt prepared by the Nippon Beer Bre-weries at Meguro, Tokyo and synthesizing, as substrates, increased number of dipeptides such. as GG, G-l-L, GA, AG, A-l-L, LA, LG, α-amino B. G., and G. α-amino butyric acid.
(2) G-l-L-splitting activity of malt extract (5% glycerin), was gradually decreased during: dialysis at 1°C against 5% glycerin under reduced pressure 80_??_100mm Hg, but was able to, be stabilized for about ore week, by the addition of conc. glycerin, making its final conc. 44%, and by being kept standing at 1°C (cf. Tables Ia and Ib).
(3) Cleavages of various peptides by dialysed malt extract thus stabilized were measured under definite conditions and calculated as percentages to the total splitting value. Remarkable differences were observed among the cleavages of these peptides. (cf. Table 2 and 3).
(4) pH-activity-curves were obtained for X_G-l-L and X_{α-amino B-G}. From these curves, it was shown that the optimal pH is 8.0 for X_G-l-L and 8.5 for X_{α-amino B-G}. (cf. Fig. 1). (cf. author's former findings, opt. pH 8.6 for X_LG and 7.8 for X_AG).
(5) Activations or inhibitions of some metal ions upon the splitting of various dipeptides were tested.
(a) X_G-l-L was remarkably activated by Co⁺⁺ and Mn⁺⁺ but inhibited by Zn⁺⁺, while Mg⁺⁺ had no influence, in 10^-3 M each metal ions. As sulphate; X_α-aminoB-G was activated by neither of these metal ions. (cf. Table 4).
(b) X_LG was activated by Mn₊₊, X_AG by Mg⁺⁺ and X_GG by Co⁺⁺, while X_GA was not activated by Zn⁺⁺, in 10^-3 M of each metal ions. (cf. Table 5)