About

Frank Raushel is a Distinguished Professor in the Department of Biochemistry and Biophysics at Texas A&M University, with a focus on enzyme catalysis, protein engineering and design, bioinformatics, catalytic detoxification, protein structure determination, new enzyme discovery, biosynthesis of complex carbohydrates, and novel enzymes from the human microbiome. His primary research program is directed at understanding how enzymes catalyze highly complex biochemical reactions with extraordinary rate enhancements and well-defined substrate profiles. He is interested in identifying high-energy intermediates and transition states of enzyme-catalyzed reactions, as well as the role of specific active site residues responsible for binding and catalysis. His work includes the development of multidisciplinary methods for discovering new enzymes capable of catalyzing novel biochemical transformations, designing approaches to reconstruct enzyme active sites, and creating new enzymes for applications such as detoxification of organophosphate nerve agents and chemo-enzymatic synthesis of antiviral therapeutics. Raushel's research also encompasses elucidating enzyme reaction mechanisms through kinetic measurements, synthesis of inhibitors, and structural studies via x-ray diffraction. His contributions include advancing the understanding of enzyme mechanisms, discovering enzymes involved in the biosynthesis of complex bacterial polysaccharides, and engineering enzymes for biotechnological applications.

Research topics

• Chemistry
• Biochemistry
• Biology
• Computer Science
• Virology
• Molecular biology
• Organic chemistry
• Materials science
• Embedded system
• Inorganic chemistry
• Nanotechnology
• Composite material

Selected publications

• Metabolic thermodynamics: pertinent reference state and energy potentials

  FEBS Journal · 2026-03-05

  articleOpen access

  Chemical potentials (molar Gibbs energies) are usually extrapolated to the remote physical–chemical reference state and then stored. Subsequent use under in vivo conditions requires a similarly substantial, reverse extrapolation, again with significant potential errors. In order to shrink both extrapolations drastically and thereby enhance both biological meaning and accuracy, we propose a transformation to a more biological reference state: pH = 7, pMg = 3, 99.5% water, with 1 m m each of the additional ‘precursors’ inorganic phosphate, sulfate, ammonium, and bicarbonate, and with twin temperatures 37 and 25 °C, ionic strength 0.15 m and m m as concentration unit. These precursors substitute for reference compounds alien to biology such as H 2 at 1 bar, and solid graphite, sulfur, and phosphorus. The standard chemical potentials are herewith increased by the magnitudes of the chemical potentials of protons, Mg 2+ , water, and the four precursors, each multiplied by the number of corresponding atoms in the molecule. This defines standard ‘metabolic potentials’. We make these potentials findable and accessible as 1360 collated standard chemical potentials for 320 compounds of biochemical interest at the twin metabolic reference states. We do this for 3 reference pH's: We present the metabolic reference state as a convenient anchor , not a universal intracellular milieu. All datasets must continue to report the actual experimental state ( T , pH, pMg, I , osmolarity, concentrations), yet aim at (also) reporting parameter values for this anchor state; we supply algorithms to transform between states. This preserves interoperability across diverse organelles, media and between enzymology and chemical engineering, while facilitating reuse.

  PublisherDOI

• Light-Triggered Accelerated Degradation of Surface-Bound Chemical Agents

  Journal of the American Chemical Society · 2026-01-30

  article

  The critical need to decontaminate surfaces from highly toxic chemical warfare agents (CWA) and the complexity of interfacial domains underscore the challenges associated with developing efficient surface cleanup technologies. To address these challenges and needs, we describe a light-switchable surface targeting microrobotic decontamination platform for accelerated biocatalytic degradation of surface-bound CWA. Biohybrid microrobots, based on Chlamydomonas reinhardtii algae, functionalized with the organophosphate-degrading enzyme phosphotriesterase (PTE), are shown to display unique light-switchable surface adhesion and gliding behaviors to offer an extremely efficient and fast surface decontamination. These biohybrid algae–PTE microrobots reversibly target hard-to-reach contaminated surfaces under blue light irradiation, while red light triggers their transition back to the bulk solution. In the surface-bound state, PTE-functionalized algae can glide collectively across the contaminated surface toward enhanced degradation efficiency. Upon completing the surface decontamination, the algae–PTE microrobots are easily released from the surface by switching to red irradiation. The applicability of the light-switchable microrobotic platform is demonstrated using a variety of contaminated surfaces, including fabrics, skin, and irregular solid surfaces, displaying surface-decontamination efficiencies higher than 90% within 5 min. Such highly efficient and rapid light-switchable surface targeting biocatalytic microrobotic platform holds considerable promise for diverse environmental surface remediation applications.

  PublisherDOI

• Identification and Functional Characterization of the Polymerizing Glycosyltransferase Required for the Transfer of <scp>d</scp>-Ribose to the <scp>d</scp>-Gal<i>f</i>NAc Moiety of the Capsular Polysaccharide of <i>Campylobacter jejuni</i>

  Biochemistry · 2025-05-01 · 3 citations

  articleOpen accessSenior authorCorresponding

  Campylobacter jejuni is the leading cause of food poisoning in the United States. The exterior surface of this bacterium is coated with a capsular polysaccharide (CPS) that helps protect the organism from the host immune system. In the HS:2 serotype of strain C. jejuni NCTC 11168, the minimal repeating trisaccharide consist of d-ribose, N-acetyl-d-galactosamine (GalNAc) and the serinol amide of d-glucuronic acid. Here we demonstrate that the C-terminal domain of Cj1432 (residues 574–914) is responsible for the transfer of d-ribose-5-P from phosphoribosyl pyrophosphate (PRPP) to C5 of the d-GalfNAc moiety of the growing polysaccharide chain. In the next step the middle domain of Cj1432 (residues 357–573) catalyzes the hydrolysis of phosphate from this product. The N-terminal domain of Cj1432 (residues 1–356) catalyzes the transfer of d-GlcA from UDP-d-GlcA to C2 of the d-ribose moiety and thus Cj1432 catalyzes three consecutive reactions during the biosynthesis of the capsular polysaccharide of C. jejuni. We have previously shown that the remaining three reactions required for the polymerization of the CPS are catalyzed by the bifunctional enzyme Cj1438 and Cj1435. We have now demonstrated that the minimal repeating trisaccharide of the CPS of C. jejuni NCTC 11168 requires six enzyme-catalyzed reactions with six intermediate structures. This accomplishment will now enable the large-scale cell-free enzyme-catalyzed synthesis of well-defined oligomers of the CPS that can potentially be used in the production of glycoconjugate vaccines for the prevention of infections by C. jejuni.

  PublisherDOI

• Functional Characterization of Two Polymerizing Glycosyltransferases for the Addition of <i>N</i>-Acetyl-<scp>d</scp>-galactosamine to the Capsular Polysaccharide of <i>Campylobacter jejuni</i>

  Biochemistry · 2025-01-24 · 2 citations

  articleOpen accessSenior authorCorresponding

  The exterior surface of the human pathogen Campylobacter jejuni is coated with a capsular polysaccharide (CPS) that consists of a repeating sequence of 2–5 different sugars that can be modified with various molecular decorations. In the HS:2 serotype from strain NCTC 11168, the repeating unit within the CPS is composed of d-ribose, N-acetyl-d-galactosamine, and a d-glucuronic acid that is further amidated with either serinol or ethanolamine. The d-glucuronic acid moiety is also decorated with d-glycero-l-gluco-heptose. Here, we show that two different GT2 glycosyltransferases catalyze the transfer of N-acetyl-d-galactosamine from UDP-NAc-d-galactosamine furanoside to the C4-hydroxyl group of the d-glucuronamide moiety at the growing end of the capsular polysaccharide chain. Catalytic activity was not observed with glycosides of d-glucuronic acid, and thus, the C6-carboxylate of the d-glucuronic acid moiety must be amidated prior to chain elongation. One of these enzymes comprises the N-terminal domain of Cj1438 (residues 1–325) and the other is from the N-terminal domain of Cj1434 (residues 1–327). These two glycosyltransferases are ∼87% identical in sequence, but it is not clear why there are two glycosyltransferases from the same gene cluster that apparently catalyze the same reaction. This discovery represents the second polymerizing glycosyltransferase that has been isolated and functionally characterized for the biosynthesis of the capsular polysaccharide in the HS:2 serotype of C. jejuni.

  PublisherDOI

• Identification of the Polymerizing Glycosyltransferase Required for the Addition of <scp>d</scp>-Glucuronic Acid to the Capsular Polysaccharide of <i>Campylobacter jejuni</i>

  Biochemistry · 2025-01-24 · 3 citations

  articleOpen accessSenior authorCorresponding

  Campylobacter jejuni is the leading cause of food poisoning in Europe and North America. The exterior surface of this bacterium is encased by a capsular polysaccharide that is attached to a diacyl glycerol phosphate anchor via a poly-Kdo (3-deoxy-d-manno-oct-2-ulosinic acid) linker. In the HS:2 serotype of C. jejuni NCTC 11168, the repeating trisaccharide consists of d-ribose, N-acetyl-d-glucosamine, and d-glucuronate. Here, we show that the N-terminal domain of Cj1432 (residues 1–356) is responsible for the reaction of the C2 hydroxyl group from the terminal d-ribose moiety of the growing polysaccharide chain with UDP-d-glucuronate as the donor substrate. This discovery represents the first biochemical identification and functional characterization of a glycosyltransferase responsible for the polymerization of the capsular polysaccharide of C. jejuni. The product of the reaction catalyzed by the N-terminal domain of Cj1432 is the substrate for the reaction catalyzed by the C-terminal domain of Cj1438 (residues 453–776). This enzyme catalyzes amide bond formation using the C6 carboxylate of the terminal d-glucuronate moiety and (S)-serinol phosphate as substrates. It is also shown that Cj1435 catalyzes the hydrolysis of phosphate from the product catalyzed by the C-terminal domain of Cj1438. These results demonstrate that amide decoration of the d-glucuronate moiety occurs after the incorporation of this sugar into the growing polysaccharide chain.

  PublisherDOI

• Identification and Characterization of the Two Glycosyltransferases Required for the Polymerization of the HS:1 Serotype Capsular Polysaccharide of <i>Campylobacter jejuni</i> G1

  Biochemistry · 2025-02-28 · 2 citations

  articleOpen accessSenior authorCorresponding

  Campylobacter jejuni is a Gram-negative pathogenic bacterium commonly found in poultry and is the leading cause of gastrointestinal infections in the United States. Similar to other Gram-negative bacteria, C. jejuni possesses an extracellular carbohydrate-based capsular polysaccharide (CPS) composed of repeating units of monosaccharides bound via glycosidic linkages. The gene cluster for serotype 1 (HS:1) of C. jejuni contains 13 different genes required for the production and presentation of the CPS. Each repeating unit within the HS:1 CPS structure contains a backbone of glycerol phosphate and d-galactose. Here, the enzyme HS1.11 was shown to catalyze the formation of CDP-(2R)-glycerol from MgCTP and l-glycerol-3-phosphate. HS1.09 was found to be a multidomain protein that catalyzes the polymerization of l-glycerol-3-phosphate and d-galactose using UDP-d-galactose and CDP-(2R)-glycerol as substrates. The domain of HS1.09 that extends from residues 286 to 703 was shown to catalyze the transfer of l-glycerol-P from CDP-glycerol to the hydroxyl group at C4 of the d-galactose moiety at the nonreducing end of the growing oligosaccharide. The transfer of d-galactose to the C2 hydroxyl group of the glycerol-phosphate moiety was shown to be catalyzed with retention of configuration by the domain of HS1.09 that extends from residues 704 to 1095. Primers as short as a single d-galactoside were accepted as initial substrates. Oligosaccharide products were isolated by ion exchange chromatography and identified by high-resolution ESI-mass spectrometry and NMR spectroscopy.

  PublisherOA PDFDOI

• Enzymatic Synthesis of an Undecorated Capsular Polysaccharide from <i>Campylobacter jejuni</i>

  Biochemistry · 2025-08-11 · 1 citations

  articleOpen accessSenior authorCorresponding

  The exterior surface of the human pathogen Campylobacter jejuni is coated with a capsular polysaccharide (CPS) that helps protect it from the host immune system. In C. jejuni NCTC 11168 the repeating linear polysaccharide is composed of d-ribose, N-acetyl-d-galactosamine and d-glucuronic acid that is further amidated with either ethanolamine or serinol. The CPS is also decorated with d-glycero-l-gluco-heptose and methyl phosphoramidate. We have now shown that the polymerization of the undecorated CPS requires the sequential activity of six unique enzymes that must act in concert with one another. The catalytic activity of these six enzymes enabled a robust synthetic strategy to be developed to facilitate the assembly and isolation of specific oligosaccharides of up to 10 units in length. Modifications to this strategy enabled the isolation of mixtures containing oligosaccharides containing at least 19 monomeric units. The oligosaccharides were isolated by anion exchange chromatography and chemically characterized using ESI mass spectrometry and 1H NMR spectroscopy. These oligosaccharides will enable the reaction mechanisms for the decoration of the capsular polysaccharides to be determined and may facilitate the development of glycoconjugate vaccines.

  PublisherDOI

• Intramolecular epistasis correlates with divergence of specificity in promiscuous and bifunctional <scp>NSAR</scp>/<scp>OSBS</scp> enzymes

  Protein Science · 2025-04-18 · 1 citations

  articleOpen access

  Understanding the functions and evolution of specificity-determining residues is essential for improving strategies to predict and design enzyme functions. Whether the function of an amino acid residue is retained during evolution depends on intramolecular epistasis, which occurs when the same residue contributes to different phenotypes in different genetic backgrounds. This study examines the relationship between epistasis and functional divergence by investigating a conserved specificity determinant in five homologs from the N-succinylamino acid racemase (NSAR)/o-succinylbenzoate synthase (OSBS) subfamily. NSAR activity originated as a promiscuous (non-biological) activity of an ancestral OSBS. Some extant NSAR/OSBS subfamily enzymes still have OSBS activity as a biological function and NSAR as a promiscuous activity, while some use both OSBS and NSAR activities as biological functions. Others use only NSAR activity as a biological function but can still catalyze the OSBS reaction as a promiscuous activity. Previously, we determined that the conserved residue R266 in Amycolatopsis sp. T-1-60 NSAR contributes to NSAR specificity by enabling K263 to act as a general acid/base catalyst. Here, we show that mutating R266 decreased relative specificity for NSAR activity in four of five NSAR/OSBS subfamily enzymes, as predicted. However, other phenotypes exhibited epistasis related to the pleiotropy of R266, including the proton exchange rate between the catalytic lysines and the substrate, the impact on OSBS activity, and thermostability. The strength of epistasis was associated with functional and evolutionary divergence of NSAR/OSBS enzymes. These results illustrate the benefits of comparing multiple homologs for understanding mechanisms of enzyme specificity.

  PublisherOA PDFDOI

• Biosynthesis of CDP-α-<scp>d</scp>-fucofuranose and CDP-β-<scp>l</scp>-6-deoxy-altrofuranose for the Capsular Polysaccharides of <i>Campylobacter jejuni</i>

  Biochemistry · 2025-08-08

  articleOpen accessSenior authorCorresponding

  Campylobacter jejuni is a Gram-negative human pathogen and is the most common cause of gastroenteritis in the United States and Europe. C. jejuni expresses a capsular polysaccharide (CPS) that enables the evasion of the host immune response and adherence to host epithelial cells. The various subspecies (serotypes) of C. jejuni are distinguished by their unique CPS repeating units. The repeating trisaccharide in the HS:41 serotype was previously found to contain l-arabinofuranose, 6-deoxy-d-altro-heptofuranose, and a third sugar, which is either d-fucofuranose or 6-deoxy-l-altrofuranose. Genome neighborhood and sequence similarity networks were employed to identify five candidate genes for the biosynthesis of d-fucofuranose and 6-deoxy-l-altrofuranose. Here, it was demonstrated that the biosynthetic pathways for both sugars are initiated by the formation of CDP-d-glucose from CTP and d-glucose-1-phosphate as catalyzed by HS41.21. This product is dehydrated by an NAD+-dependent 4,6-dehydratase (HS41.20) that produces CDP-4-keto-6-deoxy-d-glucose. The third enzyme (HS41.19) was shown to catalyze the inversion of stereochemistry at C3 and C5 using CDP-4-keto-6-deoxy-d-glucose as the substrate. The fourth enzyme (HS41.18) is an NADPH-dependent C4-reductase that catalyzes the formation of CDP-d-fucopyranose from CDP-4-keto-6-deoxy-d-glucose in the absence of the 3,5-epimerase but catalyzes the formation of CDP-6-deoxy-l-altropyranose in the presence of the epimerase. The last enzyme (HS41.17) in the pathway was shown to catalyze the FADH2-dependent interconversion of CDP-d-fucopyranose and CDP-6-deoxy-l-altropyranose to CDP-d-fucofuranose and CDP-6-deoxy-l-altrofuranose, respectively. The overall synthesis of the two possible products is governed by the catalytic activity of the epimerase, since the C4-reductase and pyranose–furanose mutase are not affected by the stereochemistry at C5.

  PublisherDOI

• The use of phosphotriesterase in the synthesis of enantiomerically pure ProTide prodrugs

  Chemico-Biological Interactions · 2025-06-06 · 1 citations

  reviewOpen accessSenior author

  -isomer, thereby facilitating the efficient preparation of either isomer of the final ProTide.

  PublisherDOI

Recent grants

• NIH Grant P01GM071790

  NIH · $30.6M · 2015

• NIH Grant R01AM030343

  NIH · $74k · 1987

• Novel Biochemical Pathways for the Metabolism of Carbohydrates in the Human gut Micriobiome

  NIH · $1.3M · 2017–2022

• NIH Grant R01DK030343

  NIH · $4.5M · 2013

• NIH Grant K04DK001366

  NIH · $213k · 1989

Frequent coauthors

• Hazel M. Holden

  University of Wisconsin–Madison

  101 shared

• Steven C. Almo

  Albert Einstein College of Medicine

  96 shared

• James B. Thoden

  University of Wisconsin–Madison

  76 shared

• А.А. Федоров

  Institute of Physics

  72 shared

• Brian K. Shoichet

  University of California, San Francisco

  59 shared

• E.V. Fedorov

  Federal Almazov North-West Medical Research Centre

  56 shared

• Richard S. Hall

  49 shared

• Dao Feng Xiang

  Texas A&M University

  48 shared

Education

• B.S.

  College of St. Thomas

  1972

• Ph.D.

  University of Wisconsin-Madison

  1976

• Other

  Pennsylvania State University

  1976