Pavla Bojarová

Bio: Pavla Bojarová is an academic researcher from Academy of Sciences of the Czech Republic. The author has contributed to research in topics: Chemistry & Glycosylation. The author has an hindex of 23, co-authored 67 publications receiving 1529 citations. Previous affiliations of Pavla Bojarová include Schiller International University & University of Melbourne.

Enzymatic Glycosylation of Small Molecules: Challenging Substrates Require Tailored Catalysts

Abstract: Glycosylation can significantly improve the physicochemical and biological properties of small molecules like vitamins, antibiotics, flavors, and fragrances. The chemical synthesis of glycosides is, however, far from trivial and involves multistep routes that generate lots of waste. In this review, biocatalytic alternatives are presented that offer both stricter specificities and higher yields. The advantages and disadvantages of different enzyme classes are discussed and illustrated with a number of recent examples. Progress in the field of enzyme engineering and screening are expected to result in new applications of biocatalytic glycosylation reactions in various industrial sectors.

Purification and characterization of a nitrilase from Aspergillus niger K10

Abstract: Aspergillus niger K10 cultivated on 2-cyanopyridine produced high levels of an intracellular nitrilase, which was partially purified (18.6-fold) with a 24% yield. The N-terminal amino acid sequence of the enzyme was highly homologous with that of a putative nitrilase from Aspergillus fumigatus Af293. The enzyme was copurified with two proteins, the N-terminal amino acid sequences of which revealed high homology with those of hsp60 and an ubiquitin-conjugating enzyme. The nitrilase exhibited maximum activity (91.6 U mg-1) at 45°C and pH 8.0. Its preferred substrates, in the descending order, were 4-cyanopyridine, benzonitrile, 1,4-dicyanobenzene, thiophen-2-acetonitrile, 3-chlorobenzonitrile, 3-cyanopyridine, and 4-chlorobenzonitrile. Formation of amides as by-products was most intensive, in the descending order, for 2-cyanopyridine, 4-chlorobenzonitrile, 4-cyanopyridine, and 1,4-dicyanobenzene. The enzyme stability was markedly improved in the presence of d-sorbitol or xylitol (20% w/v each). p-Hydroxymercuribenzoate and heavy metal ions were the most powerful inhibitors of the enzyme.

Radical S-Adenosylmethionine Enzymes

Abstract: It was once widely held that nearly all reactions in biology were catalyzed via mechanisms involving paired electron species. Beginning approximately 40 years ago, this paradigm was repeatedly challenged as examples of enzymatic reactions involving organic radical intermediates began to emerge, and it is now well accepted that biochemical reactions often involve organic radicals. Indeed, some of the most intensely studied metalloenzymes, including cytochrome P450, methane monooxygenase, ribonucleotide reductase, and the adenosylcobalamin (B12) enzymes, catalyze reactions employing organic radical intermediates. As a general rule, enzymes utilizing radical mechanisms catalyze reactions that would be difficult or impossible to catalyze by polar mechanisms, most often involving H-atom abstraction from an unactivated C–H bond. Among the more recent additions to the enzymes that catalyze radical reactions are the radical S-adenosylmethionine (radical SAM) enzymes, which were first classified as a superfamily in 2001.1 These enzymes utilize a [4Fe–4S] cluster and SAM to initiate a diverse set of radical reactions, in most or all cases via generation of a 5′-deoxyadenosyl radical (dAdo•) intermediate. Although 2001 marked the identification of this superfamily largely through bioinformatics, the discovery of iron metalloenzymes utilizing SAM to initiate radical reactions precedes this date by more than a decade. For example, early studies on the activation of pyruvate formate-lyase showed that it involved the generation of a stable protein radical,2 and was stimulated by the presence of iron, SAM, and an “activating component” from the cell extract now known to be the pyruvate-formate lyase activating enzyme (PFL-AE).3 The radical on PFL was ultimately shown to be located on a specific glycine residue,4 and was one of the first stable protein radicals characterized. PFL-AE was ultimately shown to contain a catalytically essential iron–sulfur cluster,5 and to use SAM as an essential component of PFL activation.6 The anaerobic ribonucleotide reductase, similar to PFL, contains a stable glycyl radical that was shown in early work to require an iron–sulfur cluster and SAM for activation.7 Likewise, preliminary investigations on lysine 2,3-aminomutase (LAM) published in 1970 demonstrated activation by ferrous ion and a strict requirement for SAM.8 Like PFL-AE, LAM was ultimately found to contain a catalytically essential iron–sulfur cluster.9 Work in Perry Frey’s lab showed that LAM used the adenosyl moiety of SAM to mediate hydrogen transfer in a manner similar to adenosylcobalamin-dependent rearrangements, implicating radical intermediates.10 Biotin synthase was first reported to require iron and SAM in 1995,11 and was subsequently shown to contain iron–sulfur clusters and to catalyze a radical reaction.12 These four enzyme systems (PFL/PFL-AE, aRNR, LAM, and biotin synthase) provided early indications of a new type of biological cofactor consisting of an iron–sulfur cluster and SAM, which initiate radical reactions using a fundamental new mechanism of catalysis.13 What none of us in the field in the early days probably anticipated, however, was just how ubiquitous these enzymes would turn out to be. The initial report of the superfamily by Sofia et al. identified ∼600 members;1 however, now that number is ∼48 100 members.14 These enzymes are found across the phylogenetic kingdom and catalyze an amazingly diverse set of reactions, the vast majority of which have yet to be characterized. This Review will begin by summarizing unifying features of radical SAM enzymes, and in subsequent sections delve further into the biochemical, spectroscopic, structural, and mechanistic details for those enzymes that have been characterized. In most cases, these enzymes are grouped by reaction type; however, in two cases (syntheses of modified tetrapyrroles and complex metal cluster cofactors), we have chosen to group together several radical SAM enzymes that catalyze different reaction types but which act together in the same or related metabolic pathways.

Biological applications of functionalized calixarenes

Abstract: The functionalized calixarene derivatives exhibit remarkable properties towards organic and bioorganic molecules. However, the ability of calixarene derivatives to form stable complexes with biomolecules allows them to be applied for the development of biosensors and in the field of biology, biotechnology, and drug discovery. The applications of the functionalized calixarenes are summarized in this review, and an outlook for the future developments is discussed. A brief survey (of the last 10 years) on their biological application in various fields is also considered (199 references).

A comprehensive review of glycosylated bacterial natural products.

Abstract: A systematic analysis of all naturally-occurring glycosylated bacterial secondary metabolites reported in the scientific literature up through early 2013 is presented. This comprehensive analysis of 15 940 bacterial natural products revealed 3426 glycosides containing 344 distinct appended carbohydrates and highlights a range of unique opportunities for future biosynthetic study and glycodiversification efforts.