Abstract
The endo-pectic acid transeliminase of Bacillus polymyxa was shown to attack unsaturated tetragalacturonic acid (the terminal unit on the reducing end is a 4,5-dehydrogalacturonide) only at the middle glycosidic bond (bond 2). Since unsaturated tetragalacturonic acid has a greater affinity for the enzyme and was attacked more rapidly than normal trigalacturonic acid, it was concluded that the presence of the unsaturated bond inhibited or decreased affinity of the enzyme for bond 3 but enhanced affinity for and attack of bond 2. It was shown that unsaturated trigalacturonic acid was cleaved at the bond adjacent to the unsaturated unit but apparently at a much slower rate than normal trigalacturonic acid. The Km and Vm values were determined with the following results: Km, acid soluble pectic acid < tetragalacturonic acid or unsaturated tetragalacturonic acid < trigalacturonic acid; Vm, acid soluble pectic acid > tetragalacturonic acid or unsaturated tetragalacturonic acid > trigalacturonic acid. These results support the conclusion that the transeliminase cleaves polygalacturonic acid in a random manner.
Published Version
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