The pectic enzymes of Aspergillus niger. A mercury-activated exopolygalacturonase.

1. An exopolygalacturonase was separated from a mycelial extract of Aspergillus niger with a 290-fold purification and a recovery of 8.6%. 2. The enzyme displayed its full activity only in the presence of Hg(2+) ions; K(A) for mercuric chloride was about 6x10(-8)m. 3. The mercury-activated enzyme progressively removed the terminal galacturonic acid residues from alpha-(1-->4)-linked galacturonide chains and converted digalacturonic acid, trigalacturonic acid, tetragalacturonic acid and pectic acid into galacturonic acid.