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Updated: May 19, 2026

Unraveling Entropic Rate Acceleration Induced by Solvent Dynamics in Membrane Enzymes
Published on: January 16, 2016
Uncoupling intramolecular processing and substrate hydrolysis in the N-terminal nucleophile hydrolase hASRGL1 by
Wenzong Li1, Jason R Cantor, S D Yogesha
1Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712, United States.
Abstract:
The human asparaginase-like protein 1 (hASRGL1) catalyzes the hydrolysis of l-asparagine and isoaspartyl-dipeptides. As an N-terminal nucleophile (Ntn) hydrolase superfamily member, the active form of hASRGL1 is generated by an intramolecular cleavage step with Thr168 as the catalytic residue. However, in vitro, autoprocessing is incomplete (~50%), fettering the biophysical characterization of hASRGL1. We circumvented this obstacle by constructing a circularly permuted hASRGL1 that uncoupled the autoprocessing reaction, allowing us to kinetically and structurally characterize this enzyme and the precursor-like hASRGL1-Thr168Ala variant. Crystallographic and biochemical evidence suggest an activation mechanism where a torsional restraint on the Thr168 side chain helps drive the intramolecular processing reaction. Cleavage and formation of the active site releases the torsional restriction on Thr168, which is facilitated by a small conserved Gly-rich loop near the active site that allows the conformational changes necessary for activation.
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