An Enzyme with High Catalytic Proficiency Utilizes Distal Site Substrate Binding Energy to Stabilize the Closed State but at the Expense of Substrate Inhibition

Visualizing Dynamic Weak Interaction Networks of Fluorine Atoms within Proteins via NMR

The utilization of fluorine probes in protein research has advanced our understanding of the nature of macromolecules. The diverse activities of proteins are governed by intricate weak interaction networks, yet the experimental detection presents a challenge. Herein, we have developed an NMR analytical method based on quantum coherent operations to characterize the weak chemical bonds of fluorine atoms within proteins that are bound to metal fluorides or labeled with fluorinated amino acids. Our approach offers a fast-screening method for identifying a weak interaction network without requiring crystallization.

Peri active site catalysis of proline isomerisation is the molecular basis of allomorphy in β-phosphoglucomutase

Metabolic regulation occurs through precise control of enzyme activity. Allomorphy is a post-translational fine control mechanism where the catalytic rate is governed by a conformational switch that shifts the enzyme population between forms with different activities. β-Phosphoglucomutase (βPGM) uses allomorphy in the catalysis of isomerisation of β-glucose 1-phosphate to glucose 6-phosphate via β-glucose 1,6-bisphosphate. Herein, we describe structural and biophysical approaches to reveal its allomorphic regulatory mechanism. Binding of the full allomorphic activator β-glucose 1,6-bisphosphate stimulates enzyme closure, progressing through NAC I and NAC III conformers. Prior to phosphoryl transfer, loops positioned on the cap and core domains are brought into close proximity, modulating the environment of a key proline residue. Hence accelerated isomerisation, likely via a twisted anti/C4-endo transition state, leads to the rapid predominance of active cis-P βPGM. In contrast, binding of the partial allomorphic activator fructose 1,6-bisphosphate arrests βPGM at a NAC I conformation and phosphoryl transfer to both cis-P βPGM and trans-P βPGM occurs slowly. Thus, allomorphy allows a rapid response to changes in food supply while not otherwise impacting substantially on levels of important metabolites.

Synthesis of a COF-on-MOF hybrid nanomaterial for enhanced colorimetric biosensing

The construction of hybrid materials is significant for the exploration of functionalities in colorimetric biosensing due to its structural designability and synergy effects. In this work, a COF-on-MOF hybrid nanomaterial has been newly synthesized for colorimetric biosensing. Experimental results reveal that on-surface synthesis of COF on MOF brings nanoscale proximity between COF and MOF, which exhibits more than two folds of peroxidase-like activity as compared to single Fe-MOF. Therefore, by using the MCA@Fe-MOF nanomaterial with the assist of a specific acetyl-peptide, MCA@Fe-MOF can serve as an efficient signal reporter for colorimetric assay of histone deacetylase (HDAC), and the limit of detection (LOD) can be as low as 0.261 nM. Looking forward, the demand for diverse and promising COF-on-MOF nanomaterials with varied functionalities is anticipated, propelling further exploration of their role in colorimetric biosensing.

Enhancing the Catalytic Efficiency of D-lactonohydrolase through the Synergy of Tunnel Engineering, Evolutionary Analysis, and Force-Field Calculations

Computational design advances enzyme evolution and their use in biocatalysis in a faster and more efficient manner. In this study, a synergistic approach integrating tunnel engineering, evolutionary analysis, and force-field calculations has been employed to enhance the catalytic activity of D-lactonohydrolase (D-Lac), which is a pivotal enzyme involved in the resolution of racemic pantolactone during the production of vitamin B5. The best mutant, N96S/A271E/F274Y/F308G (M3), was obtained and its catalytic efficiency (kcat/KM) was nearly 23-fold higher than that of the wild-type. The M3 whole-cell converted 20 % of DL-pantolactone into D-pantoic acid (D-PA, >99 % e.e.) with a conversion rate of 47 % and space-time yield of 107.1 g L-1 h-1, demonstrating its great potential for industrial-scale D-pantothenic acid production. Molecular dynamics (MD) simulations revealed that the reduction in the steric hindrance within the substrate tunnel and conformational reconstruction of the distal loop resulted in a more favourable"catalytic" conformation, making it easier for the substrate and enzyme to enter their pre-reaction state. This study illustrates the potential of the distal residue on the pivotal loop at the entrance of the D-Lac substrate tunnel as a novel modification hotspot capable of reshaping energy patterns and consequently influencing the enzymatic activity.

Utilization of Cofactor Binding Energy for Enzyme Catalysis: Formate Dehydrogenase-Catalyzed Reactions of the Whole NAD Cofactor and Cofactor Pieces

The pressure to optimize enzymatic rate accelerations has driven the evolution of the induced-fit mechanism for enzyme catalysts where the binding interactions of nonreacting phosphodianion or adenosyl substrate pieces drive enzyme conformational changes to form protein substrate cages that are activated for catalysis. We report the results of experiments to test the hypothesis that utilization of the binding energy of the adenosine 5'-diphosphate ribose (ADP-ribose) fragment of the NAD cofactor to drive a protein conformational change activates Candida boidinii formate dehydrogenase (CbFDH) for catalysis of hydride transfer from formate to NAD+. The ADP-ribose fragment provides a >14 kcal/mol stabilization of the transition state for CbFDH-catalyzed hydride transfer from formate to NAD+. This is larger than the ca. 6 kcal/mol stabilization of the ground-state Michaelis complex between CbFDH and NAD+ (KNAD = 0.032 mM). The ADP, AMP, and ribose 5'-phosphate fragments of NAD+ activate CbFDH for catalysis of hydride transfer from formate to nicotinamide riboside (NR). At a 1.0 M standard state, these activators stabilize the hydride transfer transition states by ≈5.5 (ADP), 5.5 (AMP), and 4.4 (ribose 5'-phosphate) kcal/mol. We propose that activation by these cofactor fragments is partly or entirely due to the ion-pair interaction between the guanidino side chain cation of R174 and the activator phosphate anion. This substitutes for the interaction between the α-adenosyl pyrophosphate anion of the whole NAD+ cofactor that holds CbFDH in the catalytically active closed conformation.

Enabling Role of Ligand-Driven Conformational Changes in Enzyme Evolution

Many enzymes that show a large specificity in binding the enzymatic transition state with a higher affinity than the substrate utilize substrate binding energy to drive protein conformational changes to form caged substrate complexes. These protein cages provide strong stabilization of enzymatic transition states. Using part of the substrate binding energy to drive the protein conformational change avoids a similar strong stabilization of the Michaelis complex and irreversible ligand binding. A seminal step in the development of modern enzyme catalysts was the evolution of enzymes that couple substrate binding to a conformational change. These include enzymes that function in glycolysis (triosephosphate isomerase), the biosynthesis of lipids (glycerol phosphate dehydrogenase), the hexose monophosphate shunt (6-phosphogluconate dehydrogenase), and the mevalonate pathway (isopentenyl diphosphate isomerase), catalyze the final step in the biosynthesis of pyrimidine nucleotides (orotidine monophosphate decarboxylase), and regulate the cellular levels of adenine nucleotides (adenylate kinase). The evolution of enzymes that undergo ligand-driven conformational changes to form active protein-substrate cages is proposed to proceed by selection of variants, in which the selected side chain substitutions destabilize a second protein conformer that shows compensating enhanced binding interactions with the substrate. The advantages inherent to enzymes that incorporate a conformational change into the catalytic cycle provide a strong driving force for the evolution of flexible protein folds such as the TIM barrel. The appearance of these folds represented a watershed event in enzyme evolution that enabled the rapid propagation of enzyme activities within enzyme superfamilies.