Regulation of β-1,3-glucanase by carbon starvation in the mycoparasite Trichoderma harzianum

The beta-1,3-glucanase system of the mycoparasitic T. harzianum, isolate T-Y, was found to be composed of at least five different enzymes. Their migration distance in acrylamide gels corresponded to peptides with molecular masses of 30-200 kDa, and they were named accordingly. The largest enzyme - G beta-1,3-200, was the most abundant when T-Y was grown with no carbon source. Its secret-ion was almost eliminated when T-Y was grown on media containing a high concentration of carbon sources such as N-acetylglucosamine (GlcNAc) or malic acid. Several isolates of T. harzianum were found to have a beta-1,3-glucanase secretion system, controlled by catabolite repression. Each isolate exhibited a different beta-1,3-glucanase profile. G beta-1,3-200 was isolated and purified: its molecular mass was approximately 75 kDa, and ifs activity was of the exo-type, specific to beta-1,3-glucan linkages. Four short peptides resulting from proteolysis of this enzyme were sequenced, and their sequences were most homologous to LAM1.3, a previously isolated beta-1,3-glucanase.