PHYSICOCHEMICAL AND CATALYTIC PROPERTIES OF 3 ENDOPOLYGALACTURONASES FROM PENICILLIUM-PINOPHILUM

Three extracellular endopolygalacturonases from extracts of solid-stat e cultures of Penicillium pinophilum, strain ii, were purified to homo geneity as judged by electrophoresis under denaturing conditions. The purified enzyme preparations are single subunit glycoproteins with pI and M(r) values as follows: PG I (3.67-4.01; 43 100), PG II (4.0; 43 1 00), PG III (5.2-7.3; 41 600). They are all active against polygalactu ronic acid, oligogalacturonates, and to a lesser extent against pectin s. Activity against the latter substrates decreases with increasing de gree of methyl esterification. PG I and PG III readily catalyze the hy drolysis of oligogalacturonates with DP > 4, whereas PG II acts effici ently only on those with DP > 5. The K(m) values (mM) for polygalactur onate are PG I (20.7), PG II (16.9), PG III (8.3); the k(cat) values ( s-1) are PG I (91), PG II (310), PG III (4130) and in each case the Hi ll coefficient is unity. Temperature and pH optima under assay conditi ons ranged from 57 to 61-degrees-C and from 4.5 to 5.0, respectively. The E(a) values (kJ mol-1) were PG I (34.3), PG II (37.2) and PG III ( 25.7). Half-life values (min) at pH 5.0, 55-degrees-C were PG I (10.6) , PG II (16.5) and PG III (9.5).