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The application of enzymes as drugs in human therapy and healthcare has grown rapidly in recent years. This chapter provides numerous examples of microbial enzymes for the effective treatment of different diseases and the most recent research on this emerging topic, including microbial enzymes useful as “clot buster” or digestive aids, for the treatment of congenital and infectious diseases, for burn debridement and fibroproliferative diseases, and for the treatment of cancer and other health disorders.

Many Gram-negative bacteria produce N-acyl-homoserine lactones (AHLs), quorum sensing (QS) molecules that can be enzymatically inactivated by quorum quenching (QQ) processes; this approach is considered an emerging antimicrobial alternative. In this study, kinetic parameters of several AHLs hydrolyzed by penicillin acylase from Streptomyces lavendulae (SlPA) and aculeacin A acylase from Actinoplanes utahensis (AuAAC) have been determined. Both enzymes catalyze efficiently the amide bond hydrolysis in AHLs with different acyl chain moieties (with or without 3-oxo modification) and exhibit a clear preference for AHLs with long acyl chains (C12-HSL > C14-HSL > C10-HSL > C8-HSL for SlPA, whereas C14-HSL > C12-HSL > C10-HSL > C8-HSL for AuAAC). Involvement of SlPA and AuAAC in QQ processes was demonstrated by Chromobacterium violaceum CV026-based bioassays and inhibition of biofilm formation by Pseudomonas aeruginosa, a process controlled by QS molecules, suggesting the application of these multifunctional enzymes as quorum quenching agents, this being the first time that quorum quenching activity was shown by an aculeacin A acylase. In addition, a phylogenetic study suggests that SlPA and AuAAC could be part of a new family of actinomycete acylases, with a preference for substrates with long aliphatic acyl chains, and likely involved in QQ processes.

Nucleoside 2′-deoxyribosyltransferases (NDTs) catalyze the cleavage of glycosidic bonds of 2′-deoxynucleosides and the following transfer of the 2′-deoxyribose moiety to acceptor nucleobases. Here, we report the crystal structures and biochemical properties of the first tetrameric NDTs: the type I NDT from the mesophilic bacterium Enterococcus faecalis V583 (EfPDT) and the type II NDT from the bacterium Desulfotalea psychrophila (DpNDT), the first psychrophilic NDT. This novel structural and biochemical data permitted an exhaustive comparative analysis aimed to shed light into the basis of the high global stability of the psychrophilic DpNDT, which has a higher melting temperature than EfPDT (58.5 °C versus 54.4 °C) or other mesophilic NDTs. DpNDT possesses a combination of unusual structural motifs not present neither in EfPDT nor any other NDT that most probably contribute to its global stability, in particular, a large aliphatic isoleucine-leucine-valine (ILV) bundle accompanied by a vicinal disulfide bridge and also an intersubunit disulfide bridge, the first described for an NDT. The functional and structural features of DpNDT do not fit the standard features of psychrophilic enzymes, which lead us to consider the implication of (sub)cellular levels together with the protein level in the adaptation of enzymatic activity to low temperatures.

In this work, a mono- and a bi-enzymatic analytical immobilized enzyme reactors (IMERs) were developed as prototypes for biosynthetic purposes and their performances in the in-flow synthesis of nucleoside analogues of pharmaceutical interest were evaluated. Two biocatalytic routes based on nucleoside 2′-deoxyribosyltransferase from Lactobacillus reuteri (LrNDT) and uridine phosphorylase from Clostridium perfrigens (CpUP)/purine nucleoside phosphorylase from Aeromonas hydrophila (AhPNP) were investigated in the synthesis of 2′-deoxy, 2′,3′- dideoxy and arabinonucleoside derivatives. LrNDT-IMER catalyzed the synthesis of 5-fluoro-2′-deoxyuridine and 5-iodo-2′-deoxyuridine in 65–59% conversion yield, while CpUP/AhPNP-IMER provided the best results for the preparation of arabinosyladenine (60% conversion yield)., Cariplo Foundation (Italy), Sección Deptal. de Bioquímica y Biología Molecular (Biológicas), Fac. de Ciencias Biológicas, TRUE, pub

There are a few PHA-producer bacteria that can uptake glycerol to produce this biopolymer. Among them, Bacillus megaterium LVN01 has demonstrated to be able to grow up using glycerol as a carbon source. Glycerol dehydrogenase (GD) plays a key role in the synthesis of PHA from glycerol. In this study, the improvement of glycerol uptake by a recombinant strain of B. megaterium carrying pHT01-bmgd was evaluated in order to enhance PHA production. The biomass and PHA production were evaluated and compared to wild-type. It was determined that the PHA produced by both strains was PHB and the highest improvement in PHB yield was 226% at 30 h.

Nineteen medium-chain-length (mcl) poly(3-hydroxyalkanoate) (PHA)-degrading microorganisms were isolated from natural sources. From them, seven Gram-positive and three Gram -negative bacteria were identified. The ability of these microorganisms to hydrolyze other biodegradable plastics, such as short-chain-length (scl) PHA, poly(ε-caprolactone) (PCL), poly(ethylene succinate) (PES), and poly(L-lactide) (PLA), has been studied. On the basis of the great ability to degrade different polyesters, Streptomyces roseolus SL3 was selected, and its extracellular depolymerase was biochemically characterized. The enzyme consisted of one polypeptide chain of 28 kDa with a pI value of 5.2. Its maximum activity was observed at pH 9.5 with chromogenic substrates. The purified enzyme hydrolyzed mcl PHA and PCL but not scl PHA, PES, and PLA. Moreover, the mcl PHA depolymerase can hydrolyze various substrates for esterases, such as tributyrin and p-nitrophenyl (pNP)-alkanoates, with its maximum activity being measured with pNP-octanoate. Interestingly, when poly(3-hydroxyoctanoate-co-3-hydroxyhexanoate [11%]) was used as the substrate, the main hydrolysis product was the monomer (R)-3-hydroxyoctanoate. In addition, the genes of several Actinobacteria strains, including S. roseolus SL3, were identified on the basis of the peptide de novo sequencing of the Streptomyces venezuelae SO1 mcl PHA depolymerase by tandem mass spectrometry. These enzymes did not show significant similarity to mcl PHA depolymerases characterized previously. Our results suggest that these distinct enzymes might represent a new subgroup of mcl PHA depolymerases.

Purification and matrix-assisted refolding of recombinant His-tagged polyhydroxyalkanoate (PhaZ) depolymerase from Pseudomonas putida KT2442 was carried out. His-tagged enzyme was overproduced as inclusion bodies in recombinant E. coli M15 (pREP4, pPAZ3), which were denatured by 8 M urea, immobilized on Ni2+-nitrilotriacetate-agarose matrix, and refolded by gradual removal of the chaotropic agent. The refolded enzyme could not be eluted with 1 M imidazole buffer, leading to an immobilized biocatalyst where PhaZ depolymerase was homogeneously distributed in the agarose support as shown by confocal scanning microscopy. Polyhydroxyoctanoate could not be hydrolyzed by this novel immobilized biocatalyst, whereas the attached enzyme was active in the hydrolysis of p-nitrophenyl alkanoate esters, which differed in their alkyl chain length. Taking advantage of the observed esterase activity on p-nitrophenylacetate, functional characterization of immobilized PhaZ depolymerase was carried out. The immobilized enzyme was more stable than its soluble counterpart and showed optimal hydrolytic activity at 37°C and 50 mM phosphate buffer pH 8.0. Kinetic parameters were obtained with both p-nitrophenylacetate and p-nitrophenyloctanoate, which had not been described so far for the soluble enzyme, representing an attractive and alternative chromogenic assay for the study of this paradigmatic enzyme

Aculeacin A acylase from Actinoplanes utahensis produced by Streptomyces lividans revealed acylase activities that are able to hydrolyze penicillin V and several natural aliphatic penicillins. Penicillin K was the best substrate, showing a catalytic efficiency of 34.79 mM−1 s−1. Furthermore, aculeacin A acylase was highly thermostable, with a midpoint transition temperature of 81.5°C.

La ciencia en muchas ocasiones se nutre de la casualidad y la buena interpretación de las señales observadas puede llegar a grandes descubrimientos. Así la casualidad hizo que en 1928, Alexander Fleming descubriese la capacidad antibacteriana delhon Penicillium notatum, tras observar y analizar la contaminación accidental de las placas de cultivos de Streptococus aureus. Posteriormente, desarrolló el hongo de un medio de cultivo líquido, observando que el exacto filtrado, libre de células, era capaz de inhibir el crecimiento de muchas especies bacterianas. Al principio activo de estos caldos lo denominó "penicilina". Fleming no pudo seguir avanzando en el estudio de la peneicilina, ya que todos los intentos llevados a cabo para su aislamiento y purificación resultaron infroructuosos debido a su inestabilidad. Fue Ernest Chain quien, diez años más tarde, en 1940, consiguió aislar y obtener una preparación estable de penicilina, así como su carazterización físico-química. Esto permitió que el grupo de Horward W. Florey desarrollase los métodos que permitieron el uso terapeútico de la penicilina, al demostrar su baja toxicidad en los animales poniendo de manifiesto su impresionante capacidad como agente bactericida en el tratamiento de enfermedades infecciosas, lo que hizo posible su utilización con gran éxito durante la Segunda Guerra Mundial y supuso el comienzo de la era de los antibióticos.