Biology; Chemistry and chemical biology; Chemical and biological engineering; Biomedical engineering
In Copyright : this Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). https://rightsstatements.org/page/InC/1.0/;
Elucidating the Unusual Reaction Kinetics of D-Glucuronyl C5-Epimerase, D. Vaidyanathan, E. Paskaleva, T. Vargason, X. Ke, S. McCallum, R. J. Linhardt, J. S. Dordick, Glycobiology, 30, 847–858, 2020.
The chemoenzymatic synthesis of heparin, through a multienzyme process, represents a critical challenge in providing a safe and effective substitute for this animal-sourced anticoagulant drug. D-glucuronyl C5-epimerase (C5-epi) is an enzyme acting on a heparin precursor, N-sulfoheparosan, catalyzing the reversible epimerization of D-glucuronic acid (GlcA) to L-iduronic acid (IdoA). The absence of reliable assays for C5-epi has limited elucidation of the enzymatic reaction and kinetic mechanisms. Real time and offline assays are described that rely on 1D 1H NMR to study the activity of C5-epi. Apparent steady-state kinetic parameters for both the forward and the pseudo-reverse reactions of C5-epi are determined for the first time using polysaccharide substrates directly relevant to the chemoenzymatic synthesis and biosynthesis of heparin. The forward reaction shows unusual sigmoidal kinetic behavior, and the pseudo-reverse reaction displays nonsaturating kinetic behavior. The atypical sigmoidal behavior of the forward reaction was probed using a range of buffer additives. Surprisingly, the addition of 25 mM each of CaCl2 and MgCl2 resulted in a forward reaction exhibiting more conventional Michaelis–Menten kinetics. The addition of 2-O-sulfotransferase, the next enzyme involved in heparin synthesis, in the absence of 3′-phosphoadenosine 5′-phosphosulfate, also resulted in C5-epi exhibiting a more conventional Michaelis–Menten kinetic behavior in the forward reaction accompanied by a significant increase in apparent Vmax. This study provides critical information for understanding the reaction kinetics of C5-epi, which may result in improved methods for the chemoenzymatic synthesis of bioengineered heparin.;
Glycobiology, 30, 847–858; Note : if this item contains full text it may be a preprint, author manuscript, or a Gold OA copy that permits redistribution with a license such as CC BY. The final version is available through the publisher’s platform.
The Linhardt Research Labs.; The Shirley Ann Jackson, Ph.D. Center for Biotechnology and Interdisciplinary Studies (CBIS);
The Linhardt Research Labs Online Collection; Rensselaer Polytechnic Institute, Troy, NY; Glycobiology; https://harc.rpi.edu/;