Cloning and Expression of a NovelTrichoderma virideLaminarinase AI Gene (lamAI)

The gene lamAI, which encodes a novel laminarinase AI of Trichoderma viride U-1, was cloned using RT-PCR in conjunction with the rapid amplification of cDNA ends (RACE) technique. The open reading frame consisted of 2,277 bp encoding a protein of 759 amino acid residues, including a 32-residue signal prepropeptide. The protein showed 91% sequence similarity to the putative Trichoderma virens beta-1,3-glucanase BGN1, but no significant similarity to fungal beta-1,6-glucanases or beta-1,3-glucanases from other organisms. On 40 h incubation with a solo carbon source, northern analysis revealed that the gene was induced by 0.5% laminaran from Eisenia bicyclis but was not by the same concentration of glucose. The lamAI cDNA was functionally expressed in the methylotrophic yeast Pichia pastoris, resulting in a recombinant enzyme with as high activity against laminaran as native LAMAI. Based on these data, the probable existence of endo-beta-1,3:1,6-glucan hydrolases as a subclass of endo-beta-1,3-glucanases in some mycoparasitic fungi is suggested.