Production Optimization and Characterization of Recombinant Cutinases from Thermobifida fusca sp. NRRL B-8184

Two genes, cut1 and cut2, of Thermobifida fusca NRRL B-8184 with cutin-hydrolyzing activity were cloned and expressed in Escherichia coli BL21 (DE3) separately. Enhanced expression was achieved after screening of six different media, optimization of the culture conditions and medium components. Among the screened media, modified Terrific Broth was found to be the best for maximum production of recombinant cutinases in E. coli BL21 (DE3). Under optimal conditions, the production of recombinant Cut1 and Cut2 (cutinases) were found to be 318?±?0.73 and 316?±?0.90 U/ml, respectively. The production of recombinant cutinases was increased by 11-fold as compared with T. fusca NRRL B-8184 wild-type strain. Both the recombinant cutinases were purified to homogeneity. They were found to be thermostable, organic solvent, and surfactant tolerant. Both the cutinase were active in a broad range of temperature (40–80 °C) and pH (6.8–9) with optimum activity at pH 8.0 and 55 °C.     

Thermostable and Alkalistable Endoxylanase of the Extremely Thermophilic Bacterium Geobacillus thermodenitrificans TSAA1: Cloning, Expression, Characteristics and Its Applicability in Generating Xylooligosaccharides and Fermentable Sugars

Xylanase encoding gene (1,224 bp) from Geobacillus thermodenitrificans was cloned in pET28a (+) vector and successfully expressed in Escherichia coli BL21 (DE3). The deduced amino acid sequence analysis revealed homology with that of glycosyl hydrolase (GH) 10 family with a high molecular mass (50 kDa). The purified recombinant xylanase is optimally active at pH 9.0 and 70 °C with T _1/2 of 10 min at 80 °C, and retains greater than 85 % activity after exposure to 70 °C for 180 min. The enzyme liberates xylose as well as xylooligosaccharides from birchwood xylan and agro-residues, and therefore, this is an endoxylanase. The xylan hydrolytic products (xylooligosaccharides, xylose, and xylobiose) find application as prebiotics and in the production of bioethanol. The xylanase being thermostable and alkalistable, it has released chromophores and phenolics from the residual lignin of pulps, suggesting its utility in mitigating chlorine requirement in pulp bleaching.     

A Xylanase Gene Directly Cloned from the Genomic DNA of Alkaline Wastewater Sludge Showing Application Potential in the Paper Industry

A xylanase gene, aws-2x, was directly cloned from the genomic DNA of the alkaline wastewater sludge using degenerated PCR and modified TAIL-PCR. The deduced amino acid sequence of AWS-2x shared the highest identity (60%) with the xylanase from Chryseobacterium gleum belonging to the glycosyl hydrolase GH family 10. Recombinant AWS-2x was expressed in Escherichia coli BL21 (DE3) and purified to electrophoretic homogeneity. The enzyme showed maximal activity at pH 7.5 and 55 °C, maintained more than 50% of maximal activity when assayed at pH 9.0, and was stable over a wide pH range from 4.0 to 11.0. The specific activity of AWS-2x towards hardwood xylan (beechwood and birchwood xylan) was significantly higher than that to cereal xylan (oat spelt xylan and wheat arabinoxylan). These properties make AWS-2x a potential candidate for application in the pulp and paper industry.     

Molecular Cloning,Characterization, and Dye-Decolorizing Ability of a Temperature- and pH-Stable Laccase from Bacillus subtilis X1

Laccases from fungal origin are typically unstable at high temperatures and alkaline conditions. This characteristic limits their practical applications. In this study, a new bacterial strain exhibiting laccase activity was isolated from raw fennel honey samples and identified as Bacillus subtilis X1. The CotA-laccase gene was cloned from strain X1 and efficiently expressed in Escherichia coli in a biologically active form. The purified recombinant laccase demonstrated an extensive pH range for catalyzing substrates and high stability toward alkaline pH and high temperatures. No loss of laccase activity was observed at pH 9.0 after 10 days of incubation, and approximately 21 % of the initial activity was detected after 10 h at 80 °C. Two anthraquinonic dyes (reactive blue 4 and reactive yellow brown) and two azo dyes (reactive red 11 and reactive brilliant orange) could be partially decolorized by purified laccase in the absence of a mediator. The decolorization process was efficiently promoted when methylsyringate was present, with more than 90 % of color removal occurring in 3 h at pH 7.0 or 9.0. These unusual properties indicated a high potential of the novel CotA-laccase for industrial applications.     

Gene Cloning,Expression, and Characterization of an Exo-inulinase from Paenibacillus polymyxa ZJ-9

An inulinase-producing strain, Paenibacillus polymyxa ZJ-9, was isolated from natural sources to produce R,R-2,3-butanediol via one-step fermentation of raw inulin extracted from Jerusalem artichoke tubers. The inulinase gene from P. polymyxa ZJ-9 was cloned and overexpressed in Escherichia coli BL21 (DE3), and the purified recombinant inulinase was estimated to be approximately 56 kDa by both sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE) and gel filtration chromatography. This result suggests that the active form of the inulinase is probably a monomer. Terminal hydrolysis fructose units from the inulin indicate that enzymes are exo-inulinase. The purified recombinant enzyme showed maximum activity at 25 °C and pH 6.0, which indicate its extreme suitability for industrial applications. Zn²⁺, Fe²⁺, and Mg²⁺ stimulated the activity of the purified enzyme, whereas Co²⁺, Cu²⁺, and Ni²⁺ inhibited enzyme activity. The K _m and V _max values for inulin hydrolysis were 1.72 mM and 21.69 μmol min^?1 mg^?1 protein, respectively. The same parameters toward sucrose were 41.09 mM and 78.7 μmol min^?1 mg^?1 protein, respectively. Considering its substrate specificity and other enzymatic characteristics, we believe that this inulinase gene from P. polymyxa ZJ-9 could be transformed into other special bacterial strains to allow inulin conversion to other biochemicals and bioenergy through one-step fermentation.     

Production of <Emphasis Type="Italic">R</Emphasis>-Mandelic Acid Using Nitrilase from Recombinant <Emphasis Type="Italic">E. coli</Emphasis> Cells Immobilized with Tris(Hydroxymethyl)Phosphine

Recombinant Escherichia coli cells harboring nitrilase from Alcaligenes faecalis were immobilized using tris(hydroxymethyl)phosphine (THP) as the coupling agent. The optimal pH and temperature of the THP-immobilized cells were determined at pH 8.0 and 55 °C. The half-lives of THP-immobilized cells measured at 35, 40, and 50 °C were 1800, 965, and 163 h, respectively. The concentration of R-mandelic acid (R-MA) reached 358 mM after merely 1-h conversion by the immobilized cells with 500 mM R,S-mandelonitrile (R,S-MN), affording the highest productivity of 1307 g L^?1 day^?1 and the space-time productivity of 143.2 mmol L^?1 h^?1 g^?1. The immobilized cells with granular shape were successfully recycled for 60 batches using 100 mM R,S-MN as substrate at 40 °C with 64% of relative activity, suggesting that the immobilized E. coli cells obtained in this study are promising for the production of R-MA.     

Cloning, Expression, and Characterization of a Recombinant Esterase from Cold-Adapted Pseudomonas mandelii

A gene coding for the extracellular esterase (EstK) was cloned from the psychrotrophic bacterium Pseudomonas mandelii based on its partial amino acid sequence as determined by mass spectrometry. The entire open reading frame consisting of 1,011 bp was expressed in Escherichia coli as a soluble protein and purified by nickel-chelated affinity chromatography and Capto Q column chromatography. Here, we show that the 33-kDa recombinant EstK protein (rEstKsp) had a substrate preference for esters of short-chain fatty acids, especially, p-nitrophenyl acetate. Optimum activity of rEstKsp was at pH 8.5 and 40 °C. The esterase activity remained similar from a range of 4～20 °C, but the maximum activity varied depending upon pH. With p-nitrophenyl acetate as the substrate, K _M was 210 μM and k _cat was 3.4 s^?1. Circular dichroism and fluorescence spectroscopy results revealed that rEstKsp had a predominantly α-helical structure and maintained its folded state at 4～40 °C. Interestingly, the tertiary structure of rEstKsp was predicted based on the structures of other hyperthermophilic esterases. Our results demonstrated that both native and rEstKsp are active at low temperatures and have a unique substrate preference for p-nitrophenyl acetate.     

Enhanced Production of Crude Violacein from Glucose in <Emphasis Type="Italic">Escherichia coli</Emphasis> by Overexpression of Rate-Limiting Key Enzyme(S) Involved in Violacein Biosynthesis

Cadaverine is used for the synthesis of the novel bio-polyamides 54, 56, and 510. Here, we examine the feasibility of using a lysine decarboxylase (LdcC) from Escherichia coli for high-level production of cadaverine. After sequential optimization of whole-cell biotransformation conditions, recombinant E. coli-overexpressing LdcC (EcLdcC) could produce 1.0 M cadaverine from 1.2 M crude l-lysine solution after 9 h. EcLdcC retained a higher cadaverine yield after being reused 10 times at acidic and alkaline pH values than that of a recombinant E. coli strain overexpressing an inducible lysine decarboxylase (CadA), a conventional cadaverine producer (90 vs. 51% at pH 6 and 55 vs. 15% at pH 8). This study reveals that EcLdcC is a promising whole-cell biocatalyst for the bio-based production of cadaverine from industrial grade l-lysine in comparison to EcCadA.     

Expression,Purification, and Characterization of NADP+-Dependent Malic Enzyme from the Oleaginous Fungus Mortierella Alpina

Malic enzymes are a class of oxidative decarboxylases that catalyze the oxidative decarboxylation of malate to pyruvate and carbon dioxide, with concomitant reduction of NAD(P)⁺ to NAD(P)H. The NADP⁺-dependent malic enzyme in oleaginous fungi plays a key role in fatty acid biosynthesis. In this study, the malic enzyme-encoding complementary DNA (cDNA) (malE1) from the oleaginous fungus Mortierella alpina was cloned and expressed in Escherichia coli BL21 (DE3). The recombinant protein (MaME) was purified using Ni-NTA affinity chromatography. The purified enzyme used NADP⁺ as the cofactor. The K _m values for l-malate and NADP⁺ were 2.19?±?0.01 and 0.38?±?0.02 mM, respectively, while the V _max values were 147?±?2 and 302?±?14 U/mg, respectively, at the optimal condition of pH 7.5 and 33 °C. MaME is active in the presence of Mn²⁺, Mg²⁺, Co²⁺, Ni²⁺, and low concentrations of Zn²⁺ rather than Ca²⁺, Cu²⁺, or high concentrations of Zn²⁺. Oxaloacetic acid and glyoxylate inhibited the MaME activity by competing with malate, and their K _i values were 0.08 and 0.6 mM, respectively.     

Characterization of a New 1,3-1,4-β-Glucanase Gene from Bacillus tequilensis CGX5-1

1,3-1,4-β-Glucanase received great interest due to its application in brewing and feed industries. Application of 1,3-1,4-β-glucanase in brewing industry helps make up for the defect that plant-derived β-glucanases are heat-sensitive. A new strain, CGX5-1, exhibited remarkable 1,3-1,4-β-glucanase, was isolated from Asian giant hornet nest and identified Bacillus tequilensis. Moreover, a new 1,3-1,4-β-glucanase gene from B. tequilensis was cloned and measured to be 720 bp encoding 239 amino acids, with a predicted molecular weight of 26.9 kDa. After expressed in Escherichia coli BL21, active recombinant enzyme of 24 kDa was detected in the supernatant of cell culture, with the activity of 2,978.2 U/mL. The new enzyme was stable in the pH 5.0–7.5 with the highest activity measured at pH 6.0. Moreover, it is thermostable within 45 to 60 °C. The property of the new recombinant enzyme makes this enzyme a broad prospect in brewing industry. Moreover, this is the first report on 1,3-1,4-β-glucanase produced by B. tequilensis.     

A Catalyst from <Emphasis Type="Italic">Burkholderia cenocepacia</Emphasis> for Efficient Anti-Prelog’s Bioreduction of 3,5-Bis(Trifluoromethyl) Acetophenone

(R)-3, 5-Bis(trifluoromethyl)phenyl ethanol is a key chiral intermediate for the synthesis of aprepitant. Through a genome mining approach, an NADPH-dependent short-chain dehydrogenases derived from Burkholderia cenocepacia (Bc-SDR) was discovered with excellent anti-Prelog’s stereoselectivity of reducing 3, 5-bis(trifluoromethyl) acetophenone. The enzyme with 247 amino acids was successfully expressed in Escherichia coli and the molecular weight was about 26 kDa. Optimization of reaction conditions showed that the optimum temperature and pH of the enzyme was 25 °C and pH 7.0, respectively. Strong enhancement of enzyme activity was observed in the presence of 1 mM Mn²⁺. In addition, Bc-SDR exhibited (R)-selective enantioselectivity toward acetophenone derivatives, which makes it a potential catalyst for obtaining aromatic chiral alcohols as useful blocks in pharmaceutical applications.     

Over-Expression of a Proline Specific Aminopeptidase from Aspergillus oryzae JN-412 and Its Application in Collagen Degradation

A strain that exhibited intracellular proline-specific aminopeptidase (PAP) activity was isolated from soy sauce koji and identified as Aspergillus oryzae JN-412. The gene coding PAP was cloned and efficiently expressed in Escherichia coli BL21 in a biologically active form. The highest specific activity reached 52.28 U mg^?1 at optimum cultivation conditions. The recombinant enzyme was purified 3.3-fold to homogeneity with a recovery of 36.7 % from cell-free extract using Ni-affinity column chromatography. It appeared as a single protein band on SDS-PAGE with molecular mass of approximately 50 kDa. The purified enzyme exhibited the highest activity at 60 °C and pH 7.5. The enzyme activity was inhibited by PMSF and ions like Zn²⁺ and Cu²⁺. DTT, β-mercaptoethanol, EDTA, and ions like Co²⁺, Mg²⁺, Mn²⁺, and Ca²⁺ had no influence on enzyme activity, whereas Ni²⁺ enhanced the enzyme activity. By using collagen as a substrate, the purified recombinant prolyl aminopeptidase contributed to the hydrolysis of collagen when used in combination with neutral protease, and free amino acids in collagen hydrolysates was significantly increased.     

Acetaldehyde Detoxification Using Resting Cells of Recombinant Escherichia coli Overexpressing Acetaldehyde Dehydrogenase

Acetaldehyde dehydrogenase (E.C. 1.2.1.10) plays a key role in the acetaldehyde detoxification. The recombinant Escherichia coli cells producing acetaldehyde dehydrogenase (ist-ALDH) were applied as whole-cell biocatalysts for biodegradation of acetaldehyde. Response surface methodology (RSM) was employed to enhance the production of recombinant ist-ALDH. Under the optimum culture conditions containing 20.68 h post-induction time, 126.75 mL medium volume and 3 % (v/v) inoculum level, the maximum ist-ALDH activity reached 496.65?±?0.81 U/mL, resulting in 12.5-fold increment after optimization. Furthermore, the optimum temperature and pH for the catalytic activity of wet cells were 40 °C and pH 9.5, respectively. The biocatalytic activity was improved 80 % by permeabilizing the recombinant cells with 0.075 % (v/v) Triton X-100. When using 2 mmol/L NAD⁺ as coenzyme, the permeabilized cells could catalyze 98 % of acetaldehyde within 15 min. The results indicated that the recombinant E. coli with high productivity of ist-ALDH might be highly efficient and easy-to-make biocatalysts for acetaldehyde detoxification.     

Production of Extremely Alkaliphilic, Halotolerent, Detergent, and Thermostable Mannanase by the Free and Immobilized Cells of Bacillus halodurans PPKS-2. Purification and Characterization

The alkaliphilic Bacillus halodurans strain PPKS-2 was shown to produce extracellular extreme alkaliphilic, halotolerent, detergent, and thermostable mannanase activity. The cultural conditions for the maximum enzyme production were optimized with respect to pH, temperature, NaCl, and inexpensive agro wastes as substrates. Mannanase production was enhanced more than 4-fold in the presence of 1 % defatted copra meal and 0.5 % peptone or feather hydrolysate at pH 11 and 40 °C. Mannanase was purified to 10.3-fold with 34.6 % yield by ion exchange and gel filtration chromatography methods. Its molecular mass was estimated to be 22 kDa by SDS-PAGE. The mannanase had maximal activity at pH 11 and 70 °C. This enzyme was active over a broad range of NaCl (0–16 %) and thermostable retaining 100 % of the original activity at 70 °C for 3 h. Immobilization of whole cells proved to be effective for continuous production of mannanase. Since the strain PPKS-2 grows on cheaper agro wastes such as defatted copra meal, corn husk, jowar bagasse, and wheat bran, these can be exploited for mannanase production on an industrial scale.     

Expression, High Cell Density Culture and Purification of Recombinant EC-SOD in Escherichia coli

Superoxide dismutase (SOD) catalyzes the dismutation of the biologically toxic superoxide anion into oxygen and hydrogen peroxide and is deployed by the immune system to kill invading microorganisms. Extracellular SOD (EC-SOD) is a copper- and zinc-containing glycoprotein found predominantly in the soluble extracellular compartment that consists of ～30-kDa subunits. Here, we purified recombinant EC-SOD3 (rEC-SOD) from Escherichia coli BL21(DE3) expressing a pET-SOD3-1 construct. Cells were cultured by high-density fed-batch fermentation to a final OD₆₀₀ of 51.8, yielding a final dry cell weight of 17.6 g/L. rEC-SOD, which was expressed as an inclusion body, comprised 48.7% of total protein. rEC-SOD was refolded by a simple dilution refolding method and purified by cation-exchange and reverse-phase chromatography. The highly purified rEC-SOD thus obtained was a mixture of monomers and dimers, both of which were active. The molecular weights of monomeric and dimeric rEC-SOD were 25,255 and 50,514 Da, respectively. The purified rEC-SOD had 4.3 EU/mg of endotoxin and the solubility of rEC-SOD was more than 80% between pH 7 and 10. In 2 L of fed-batch fermentation, 60 mg of EC-SOD (99.9% purity) could be produced and total activity was 330.24 U. The process established in this report, involving high-cell-density fermentation, simple dilution refolding, and purification with ion-exchange and reverse-phase chromatography, represents a commercially viable process for producing rEC-SOD.     

Development of a practical biocatalytic process for (S)-N-Boc-3-hydroxypiperidine synthesis

(S)-N-Boc-3-hydroxypiperidine ((S)-NBHP) is an important chiral intermediate for the synthesis of ibrutinib, an anticancer drug targeting B-cell malignancies. An NADPH-dependent reductase (YDR541C) from Saccharomyces cerevisiae was isolated and found to show excellent catalytic activity in the production of (S)-NBHP. The reductase YDR541C was cloned and overexpressed in Escherichia coli BL21 (DE3), purified to homogeneity, and its catalytic properties were studied. Furthermore, an ethyl caprylate-water (1:1, v/v) biphasic system was introduced to alleviate product inhibition. After optimization of the reaction, as much as 1200 mM N-Boc-piperidin-3-one (NBPO) (240 g/L) was asymmetrically reduced to (S)-NBHP within 6 h, resulting in a yield of 99%, an enantioselectivity of >99.5% ee, and a total turnover number (TTN) of 8000. These results indicate great potential for industrial application.     

Purification and Applications of a Lectin from the Mushroom Gymnopilus spectabilis

A lectin was isolated from fruiting bodies of the mushroom Gymnopilus spectabilis (GSL) by ionic exchange chromatography. The lectin agglutinates mouse red cells exhibiting broad specificity towards several monosaccharides including the N-acetylneuraminic acid. Agglutination was also inhibited by the glycoproteins: fetuin, lactoferrin, and recombinant erythropoietin. GSL is a glycoprotein possessing 16 % of carbohydrates; the SDS-PAGE showed two bands with molecular mass of 52.1 and 64.4 kDa. Isoelectric focusing displayed microheterogeneity, with two bands at pIs 5.1 and 5.3. The lectin was stable between pH 2 and pH 8 while at pH 10, the agglutination decayed to 50 % of initial activity. Incubation at 40 and 80 °C led to 50 and 100 % loss in activity of the lectin, respectively. Synthesized GSL-Sepharose interacts with serum pregnant mare gonadotropin, and at least two subpopulations of this glycoprotein were separated. There was no interaction between transferrin and soluble GSL while a partial recognition was achieved with GSL-Sepharose. The terminal sialic acid seems to play an active role in modifying the interaction with GSL, depending if the lectin is in a soluble or immobilized form. The purified lectin inhibited in vitro the growth of Staphylococcus aureus and Aspergillus niger.     

Purification and Characterization of a Zinc-Dependent Cinnamyl Alcohol Dehydrogenase from Leucaena leucocephala,a Tree Legume

A cinnamyl alcohol dehydrogenase (CAD) from the secondary xylem of Leucaena leucocephala has been purified to homogeneity through successive steps of ammonium sulfate fractionation, DEAE cellulose, Sephadex G-75, and Blue Sepharose CL-6B affinity column chromatographies. CAD was purified to 514.2 folds with overall recovery of 13 % and specific activity of 812. 5 nkat/mg. Native and subunit molecular masses of the purified enzyme were found to be ～76 and ～38 kDa, respectively, suggesting it to be a homodimer. The enzyme exhibited highest catalytic efficiency (Kcat/Km 3.75 μM^?1 s^?1) with cinnamyl aldehyde among all the substrates investigated. The pH and temperature optima of the purified CAD were pH 8.8 and 40 °C, respectively. The enzyme activity was enhanced in the presence of 2.0 mM Mg²⁺, while Zn²⁺ at the same concentration exerted an inhibitory effect. The inclusion of 2.0 mM EDTA in the assay system activated the enzyme. The enzyme was inhibited with caffeic acid and ferulic acid in a concentration-dependent manner, while no inhibition was observed with salicylic acid. Peptide mass analysis of the purified CAD by MALDI-TOF showed a significant homology to alcohol dehydrogenases of MDR superfamily.     

Exploring Thermophilic Cellulolytic Enzyme Production Potential of Aspergillus fumigatus by the Solid-State Fermentation of Wheat Straw

Cellulases can be used for biofuel production to decrease the fuel crises in the world. Microorganisms cultured on lignocellulosic wastes can be used for the production of cellulolytic enzymes at large scale. In the current study, cellulolytic enzyme production potential of Aspergillus fumigatus was explored and optimized by employing various cultural and nutritional parameters. Maximum endoglucanase production was observed after 72 h at 55 °C, pH 5.5, and 70 % moisture level. Addition of 0.3 % of fructose, peptone, and Tween-80 further enhanced the production of endoglucanase. Maximum purification was achieved with 40 % ammonium sulfate, and it was purified 2.63-fold by gel filtration chromatography. Endoglucanase has 55 °C optimum temperature, 4.8 optimum pH, 3.97 mM K _m, and 8.53 μM/mL/min V _max. Maximum exoglucanase production was observed at 55 °C after 72 h, at pH 5.5, and 70 % moisture level. Further addition of 0.3 % of each of fructose, peptone, and Tween-80 enhances the secretion of endoglucanase. It was purified 3.30-fold in the presence of 40 % ammonium sulfate followed by gel filtration chromatography. Its optimum temperature was 55 °C, optimum pH was 4.8, 4.34 mM K _m, and 7.29 μM/mL/min V _max. In the case of β-glucosidase, maximum activity was observed after 72 h at 55 °C, pH 5.5, and 70 % moisture level. The presence of 0.3 % of fructose, peptone, and Tween-80 in media has beneficial impact on β-glucosidase production. A 4.36-fold purification was achieved by 40 % ammonium sulfate precipitation and gel filtration chromatography. Optimum temperature of β-glucosidase was 55 °C, optimum pH was 4.8, K _m was 4.92 mM, and V _max 6.75 μM/mL/min. It was also observed that fructose is better than glucose, and peptone is better than urea for the growth of A. fumigatus. The K _m and V _max values indicated that endoglucanase, exoglucanase, and β-glucosidase have good affinity for their substrates.     

Overproduction,Purification and Characterization of Adenylate Deaminase from <Emphasis Type="Italic">Aspergillus oryzae</Emphasis>

Adenylate deaminase (AMPD, EC 3.5.4.6) is an aminohydrolase that widely used in the food and medicine industries. In this study, the gene encoding Aspergillus oryzae AMPD was cloned and expressed in Escherichia coli. Induction with 0.75 mM isopropyl β-d-l-thiogalactopyranoside resulted in an enzyme activity of 1773.9 U/mL. Recombinant AMPD was purified to electrophoretic homogeneity using nickel affinity chromatography, and its molecular weight was calculated as 78.6 kDa. Purified AMPD exhibited maximal activity at 35 °C, pH 6.0 and 30 mM K⁺, with apparent K _m and V _max values of 2.7 × 10^?4 M and 77.5 μmol/mg/min under these conditions. HPLC revealed that recombinant AMPD could effectively catalyse the synthesis of inosine-5′-monophosphate (IMP) with minimal by-products, indicating high specificity and suggesting that it could prove useful for IMP production.