Lasso peptide isopeptidase that specifically hydrolyzes Astexin-2 and Astexin-3, converting them to linear peptides (PubMed:23862624). Has only a few specific contacts with subrates, because it recognizes Astexin knotted structure (principally the loop structure) (PubMed:26534965, PubMed:27998080). Its binding to lasso peptides opens them to expose the isopeptide bonds for hydrolysis (PubMed:27998080).