The Catalytic Reaction Mechanism of the β-Galactocerebrosidase Enzyme Deficient in Krabbe Disease

Abstract

Krabbe disease is a neurodegenerative disorder related to misfunction of β-galactocerebrosidase (GALC), a glycosidase that catalyzes the cleavage of β-galactosidic bonds in glycosphingolipids. Here we uncover the catalytic molecular mechanism of GALC using quantum mechanics/molecular mechanics methods. Our results clarify the unusual chair conformation of the substrate observed in the crystal structure and show that catalysis can take place via two distinct conformational pathways (1S3 → [4H3]‡ → 4C1 and 4C1 → [4H3]‡ → 4C1) with similar free energy barriers because of leaving group flexibility. This mechanistic insight will aid in the design of Krabbe diagnosis probes and GALC conformational chaperones.