Cleaves the 2'-5' phosphodiester linkage at the branch point of excised lariat intron RNA and converts them into linear molecules that can be subsequently degraded, thereby facilitating ribonucleotide turnover (PubMed:10982890, PubMed:16232320). Linked to its role in pre-mRNA processing mechanism, may also participate in retrovirus replication via an RNA lariat intermediate in cDNA synthesis and have an antiviral cell-intrinsic defense function in the brainstem (PubMed:16232320, PubMed:29474921). Optimum pH is 7.0. Ubiquitously expressed, strongest expression in the spinal cord and brainstem. Disease susceptibility is associated with variants affecting the gene represented in this entry. Belongs to the lariat debranching enzyme family.