Purification and Certain Properties of Pectin Trans-eliminase from Aspergillus Fonsecaeus.

In 1960 Albersheim, Neukom, and Deuel (1) reported on an enzyme present in a commercial pectic enzyme preparation (Pectin01 RlO, Rohm and Haas Company, Philadelphia) that degraded the a, 1 + 4-glycokidic bonds in pectin by a trans elimination of the proton on the 5th carbon atom of an anhydromethyl galacturonate unit with the oxygen of the adjacent glycosidic bond. Cleavage of the bonds in pectin resulted in the formation of esters of galacturonides of undetermined size with unsaturated bonds between carbon atoms 4 and 5 at the nonreducing ends of the fragments formed. These double bonds strongly absorbed light at 235 mp. The enzymatic process was thought to occur by a reaction mechanism similar to that of the degradation of pectin in neutral (2) or in alkaline (3) solutions. In a more recent publication (4), the purification of pectin truns-eliminase of Pectin01 R-10 was described. By the use of diethylaminoethyl cellulose chromatography, Sephadex gel filtration, and isoelectric precipitation, a 22-fold purification was obtained, although the removal of polygalacturonase and pectinesterase from the purified enzyme was not demonstrated. Similar enzymes, which are specific for polygalacturonic acid, have been reported in cultures of Bacillus polymyxa (5, 6) and in species of Erwinia (7, 8). The present work describes the production of pectin truns-eliminase by Aspergillus fonsecaeus, a fungus which formed this enzyme extracellularly in significant amounts. The purification and some of the properties of pectin trans-eliminase are reported, and it will be shown that this enzyme differs in several respects from bacterial polygalacturonic acid truns-eliminase.