SEPARATION AND LIMITED CHARACTERIZATION OF 3 POLYGALACTURONASES OF ASPERGILLUS-NIGER

A strain of Aspergillus niger isolated from onion, when cultured in a medium containing onion, glucose, and salt, secreted large amounts of polygalacturonase (PG). A simple and rapid three-step procedure was adopted to separate the extracellular PG into endo- and exo- forms. The method gave an overall yield of 47%. Determination of the reducing groups at a 50% decrease in the relative viscosity of 1% sodium polypectate (NaPP) as substrate revealed the presence of two exo- forms (PGI and PGII) and one endo- form (PGIII). All three forms of the enzyme were optimally active at pH 5.0 and preferred NaPP as a substrate over pectin. K(m) values for Napp were 0.24, 0.12, and 0.063% for PGI, PGII, and PGIII, respectively