Synthesis of an antiviral drug precursor from chitin using a saprophyte as a whole-cell catalyst

Steiger, Mach-Aigner, Gorsche Rita, Rosenberg, Mihovilovic, Mach

Description

Recent incidents, such as the SARS and influenza epidemics, have highlighted the need for readily available antiviral drugs. One important precursor currently used for the production of Relenza, an antiviral product from GlaxoSmithKline, is N-acetylneuraminic acid (NeuNAc). This substance has a considerably high market price despite efforts to develop cost-reducing (biotechnological) production processes. Hypocrea jecorina ( Trichoderma reesei ) is a saprophyte noted for its abundant secretion of hydrolytic enzymes and its potential to degrade chitin to its monomer N-acetylglucosamine (GlcNAc). Chitin is considered the second most abundant biomass available on earth and therefore an attractive raw material. Results In this study, we introduced two enzymes from bacterial origin into Hypocrea , which convert GlcNAc into NeuNAc via N-acetylmannosamine. This enabled the fungus to produce NeuNAc from the cheap starting material chitin in liquid culture. Furthermore, we expressed the two recombinant enzymes as GST-fusion proteins and developed an enzyme assay for monitoring their enzymatic functionality. Finally, we demonstrated that Hypocrea does not metabolize NeuNAc and that no NeuNAc-uptake by the fungus occurs, which are important prerequisites for a potential production strategy. Conclusions This study is a proof of concept for the possibility to engineer in a filamentous fungus a bacterial enzyme cascade, which is fully functional. Furthermore, it provides the basis for the development of a process for NeuNAc production as well as a general prospective design for production processes that use saprophytes as whole-cell catalysts.

Informations

• Publié par: biomed
• Publié le: 01 janvier 2011
• Nombre de lectures: 19
• Langue: English

Extrait

Steigeret al.Microbial Cell Factories2011,10:102 http://www.microbialcellfactories.com/content/10/1/102

R E S E A R C H

Open Access

Synthesis of an antiviral drug precursor from chitin using a saprophyte as a wholecell catalyst 1,4†1†31 2 Matthias G Steiger , Astrid R MachAigner , Rita Gorsche , Erwin E Rosenberg , Marko D Mihovilovic and 1* Robert L Mach

Abstract Background:Recent incidents, such as the SARS and influenza epidemics, have highlighted the need for readily available antiviral drugs. One important precursor currently used for the production of Relenza, an antiviral product from GlaxoSmithKline, is Nacetylneuraminic acid (NeuNAc). This substance has a considerably high market price despite efforts to develop costreducing (biotechnological) production processes.Hypocrea jecorina(Trichoderma reesei) is a saprophyte noted for its abundant secretion of hydrolytic enzymes and its potential to degrade chitin to its monomer Nacetylglucosamine (GlcNAc). Chitin is considered the second most abundant biomass available on earth and therefore an attractive raw material. Results:In this study, we introduced two enzymes from bacterial origin intoHypocrea, which convert GlcNAc into NeuNAc via Nacetylmannosamine. This enabled the fungus to produce NeuNAc from the cheap starting material chitin in liquid culture. Furthermore, we expressed the two recombinant enzymes as GSTfusion proteins and developed an enzyme assay for monitoring their enzymatic functionality. Finally, we demonstrated thatHypocrea does not metabolize NeuNAc and that no NeuNAcuptake by the fungus occurs, which are important prerequisites for a potential production strategy. Conclusions:This study is a proof of concept for the possibility to engineer in a filamentous fungus a bacterial enzyme cascade, which is fully functional. Furthermore, it provides the basis for the development of a process for NeuNAc production as well as a general prospective design for production processes that use saprophytes as wholecell catalysts.

Background NeuNAc is the most prevalent exponent of sialic acids [1]. In mammals, sialic acids are usually found as terminal residues of glycol conjugates on the outermost cell surface. As a result of their location and their negative carboxylate functionality, sialic acids play important roles in mediating cellular recognition and adhesion processes [2] and in the infection cycles of severe viral diseases, such as influenza viruses A and B [3]. In these cases,de novosynthesized viral particles attach to their respective sialic acids at the cell surface. Neuraminidase (sialidase) activity is needed for the propagation of the virus in the host. Consequently,

* Correspondence: [e-mail] †Contributed equally 1 Gene Technology and Applied Biochemistry, Institute of Chemical Engineering, Vienna University of Technology, Gumpendorfer Str. 1a, A1060 Wien, Austria Full list of author information is available at the end of the article

sialic acid derivatives are successfully applied in the ther apy of such virusrelated diseases. One wellknown pro duct that functions as a neuraminidase inhibitor is Relenza. Its active pharmaceutical ingredient is Zanamivir, which is a direct derivative of the NeuNAc precursor [4]. Traditionally, NeuNAc is prepared through extraction from natural sources, such as bird nests, milk, or eggs [5], through the hydrolysis of colominic acid (a homopolymer of NeuNAc) in a culture broth ofEscherichia coliK1 [6], or through chemical synthesis [7]. Methods for NeuNAc production have included a chemoenzymatic process [8,9], a twoenzyme reaction process [10,11], a biotransfor mation process usingE. coli[12], and anE. coliwholecell system [13]. However, the requirement for ATP or an excess of pyruvate and the subsequent expensive down stream processing has kept the costs of NeuNAc produc tion considerably high (current market price is $100/g).

© 2011 Steiger et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.