Peptide isomerase that inverts the chirality at the Ser-81 of omega-Aga IVB. Acts cofactor-independently. Heterodimer with venom peptide isomerase light chain; disulfide-linked. Expressed by the venom gland. N-linked glycan at Asn-127 consists of Man3-GlcNAc2-Fuc. Belongs to the peptidase S1 family.