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Palladium-mediated enzyme activation suggests multiphase initiation of glycogenesis

DOI: 10.1038/s41586-018-0644-7 DOI Help

Authors: Matthew K. Bilyard (University of Oxford) , Henry J. Bailey (Structural Genomics Consortium, University of Oxford) , Lluís Raich (Universitat de Barcelona) , Maria A. Gafitescu (University of Oxford) , Takuya Machida (University of Oxford) , Javier Iglésias-fernández (Universitat de Barcelona) , Seung Seo Lee (University of Oxford) , Christopher D. Spicer (University of Oxford) , Carme Rovira (Universitat de Barcelona; Institució Catalana de Recerca i Estudis Avançats (ICREA)) , Wyatt W. Yue (Structural Genomics Consortium, University of Oxford) , Benjamin G. Davis (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature , VOL 441

State: Published (Approved)
Published: October 2018

Abstract: Biosynthesis of glycogen, the essential glucose (and hence energy) storage molecule in humans, animals and fungi1, is initiated by the glycosyltransferase enzyme, glycogenin (GYG). Deficiencies in glycogen formation cause neurodegenerative and metabolic disease2,3,4, and mouse knockout5 and inherited human mutations6 of GYG impair glycogen synthesis. GYG acts as a ‘seed core’ for the formation of the glycogen particle by catalysing its own stepwise autoglucosylation to form a covalently bound gluco-oligosaccharide chain at initiation site Tyr 195. Precise mechanistic studies have so far been prevented by an inability to access homogeneous glycoforms of this protein, which unusually acts as both catalyst and substrate. Here we show that unprecedented direct access to different, homogeneously glucosylated states of GYG can be accomplished through a palladium-mediated enzyme activation ‘shunt’ process using on-protein C–C bond formation. Careful mimicry of GYG intermediates recapitulates catalytic activity at distinct stages, which in turn allows discovery of triphasic kinetics and substrate plasticity in GYG’s use of sugar substrates. This reveals a tolerant but ‘proof-read’ mechanism that underlies the precision of this metabolic process. The present demonstration of direct, chemically controlled access to intermediate states of active enzymes suggests that such ligation-dependent activation could be a powerful tool in the study of mechanism.

Journal Keywords: Bioconjugate chemistry; Glycosylation; Metabolism

Subject Areas: Chemistry, Biology and Bio-materials

Instruments: I03-Macromolecular Crystallography