Intracellular precursors of endo-β-1,4-glucanase in Trichoderma reesei

Abstract Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) followed by immunoblotting was employed to detect intracellular precursors of endo-β-1,4-glucanases (EGs) in Trichoderma reesei QM9414 under conditions of de novo induction by sophorose and de novo carbon catabolite derepression by lactose. Secretion of EGs was always preceded by intracellular accumulation of lower M _r precursors, which became processed to larger M _r forms immediately prior to their extracellular appearance. Treatment of the larger M _r forms with α-mannosidase converted them to forms with the same M _r as the smaller forms, whereas Endo H treatment was without effect. These results are consistent with a requirement of O -linked glycosylation for secretion of EGs by T. reesei .