Pectin transeliminase complex from Aspergillus flavus.

Aspergillus flavus grown in a liquid medium containing pectin as the sole carbon source produced extracellular enzymes which degraded the 1,4-alpha-D-glycosidic bonds of pectin. The products of degradation were characteristic of substances produced by transeliminase. Synthesis of this enzyme was repressed by the addition of sucrose, glucose, fructose and maltose. The crude enzyme was partially purified by a combination of ultrafiltration and ammonium sulfate precipitation. The partially purified enzyme was separated by molecular exclusion chromatography into three components A, B and C, with molar masses ranging from 13.2 to 64 kDa. Only fraction B exhibited enzymic activity and further fractionated by ion-exchange chromatography into four components I-IV. Among these components, only fractions I and II possessed transeliminase activity. Both fractions had an optimum activity at pH 8.5 and 35 degrees C, and were stimulated by Ca2+, Mg2+, Na+ and K+ but inhibited by EDTA and DNP. The apparent Km for the degradation of pectin by fractions I and II were 6.2 and 8.0 g/L, respectively.