抄録
Pectic glycosidases produced by a strain of Aspergillus niger comprise at least two kinds of polygalacturonases, each of which is formed in different ways depending on the culture conditions, especially on the kinds of C-sources. The one, depolymeric polygalacturonase (DPG), produced constitutively by the mold, attacks the polygalacturonase chain at random, reducing the molecular size rapidly, and leaving tri-, di- and D-galacturonic acids as end products in the final reaction mixture where more than 50% of the substrate is hardly hydrolyzed. This enzyme was effectively purified by adsorption onto pulpified filter paper, followed by the general method of precipitation, from the culture liquor which did not contain pectic substrate and other adaptive pectic enzymes. DPG is easily adsorbed in a salt-free state at a pH near 4 and eluted with a more neutral salt-solution. The reaction pH has the optimum value of 3.4-4.6, variable with the substrate and with the method of determination. DPG is most stable at pH 3.6, where the half activity is reduced by treatment at 50° for 1hour. This enzyme seems to hydrolyze the non methoxylated glycosidic chain. The another polygalacturonase, galacturonogenic polygalacturonase (GPG), the formation of which is induced by the pectic substrate in contrast to DPG, splits the terminal galacturonic acid from one end of the polygalacturonide chain, not reducing the molecular size of the substrate as rapidly as DPG does. Other properties of GPG are similar to those of DPG though there are some differences which might be due to the lesser purity.
