Exopectic Acid Transeliminase of an Erwinia

A species of Erwinia was found to produce no other pectolytic enzyme than the two transeliminases of exo-types, namely, an oligogalacturonide transeliminase and an exopectic acid transeliminase. Of the two enzymes, the exopectic acid transeliminase was isolated and its properties were investigated. The results are as follows: (1) Pectic acids having an unsaturated galacturonic acid residue at the non-reducing end of the molecule are susceptible but oxidized or reduced pectic acids resistant to the enzyme action. (2) The enzyme has no activity toward pectinic acid and polymethylpolygalacturonate methyl glycoside. The limit of the enzymatic degradation for citrus pectic acid is 43.8%. (3) The rate of the enzyme activity was maximal with tetragalacturonic acid and followed by acid-soluble pectic acid, acid-insoluble pectic acid, pectic acid and trigalacturonic acid. Unlike the oligogalacturonide transeliminases of Pseudomonas sp. (strain S2) and Erwinia aroideae, the present enzyme shows a considerably high activity toward pectic acids of high molecular weight. (4) The pH-activity curves vary with the buffer employed. (5) The enzyme is activated by Co²⁺ and Mn²⁺ but powerfully inhibited by Cu²⁺ and Hg²⁺. Ca²⁺ has no significant effect on the enzyme activity.