The present invention provides a modified botulinum neurotoxin A (BoNT/A) L-chain protease that demonstrates enhanced cleaveage of human SNAP-23 (hSNAP-23) relative to unmodified (wild-type) BoNT/A L-chain protease, together with the use thereof for cleaving hSNAP-23.本發明提供一種經修飾的肉毒桿菌神經毒素A(BoNT/A)L鏈蛋白酶,相對於未經修飾的(野生型)BoNT/A L鏈蛋白酶,其顯示增強的裂解人類SNAP-23(hSNAP-23),以及其用於裂解hSNAP-23之用途。