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Asymmetric Reduction of C=N Bonds by Imine Reductases and Reductive Aminases
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
Matthias Höhne, Philipp Matzel, Martin Gand
The exact role and necessity of the active site residue Asp/Tyr 187 is not precisely understood today. On the one hand, the active site tyrosine/aspartate seems to be important for various IREDs, because after their substitution to apolar residues IRED activities were substantially reduced, but not eliminated (Scheller et al., 2014; Man et al., 2015). On the other hand, a small fraction of functional IREDs exist with residues other than tyrosine or aspartate: Imine reductases from Saccharomonospora xinjiangensis (IR_6) has a phenylalanine (Wetzl et al., 2015).IRED from Pseudomonas putida (PDB code 3L6D) features an alanine residue in the position of the active site. Interestingly, a histidine residue lies one turn upstream. Substitution to valine showed ten-fold reduced specific residual activity, indicating a contribution of this histidine for catalysis (Gand et al., 2014).Asparagine is found in the IRED from Amycolatopsis orientalis. Furthermore, in the ternary complex with bound NADPH and 1-methyl-1,2,3,4-tetrahydroisoquinoline, this residue lies relatively remote from the imine nitrogen, so that a role in imine protonation in other IREDs can be questioned (Aleku et al., 2016).
Rifampicin (Rifampin)
Published in M. Lindsay Grayson, Sara E. Cosgrove, Suzanne M. Crowe, M. Lindsay Grayson, William Hope, James S. McCarthy, John Mills, Johan W. Mouton, David L. Paterson, Kucers’ The Use of Antibiotics, 2017
C. Alan, C. Street, Tony M. Korman
In 1957, a new class of antibiotics called rifamycins was recognized at Lepetit Laboratories in Italy. These antibiotics were isolated from Amycolatopsis (previously Streptomyces and Nocardia) mediterranei. The name “rifamycin” was derived from the 1955 French movie Rififi (Sensi, 1983). Chemical modifications to one of the original compounds, designated rifamycin B, resulted in others with increased antibacterial activity. Two of these were introduced for clinical use in some countries, rifamycin SV in 1963 and rifamycin B diethylamide, or rifamide, in 1965; both were active against Mycobacterium tuberculosis and various other bacteria, but they were rapidly excreted by the liver and required parenteral administration. Further chemical modifications of rifamycin were made with the aim of producing a drug which was absorbed after oral administration, had a more prolonged antibacterial level in the blood, and had greater activity against mycobacteria and other bacteria. Rifampicin (also called rifampin) was synthesized in 1965 and introduced for clinical use in 1968. The name rifampin is used in the United States, while the drug is called rifampicin in Europe and Australia. Rifampicin has the chemical formula of 3–4 (4-methylpiperazinyl-iminomethylidene)-rifamycin SV (Sensi et al., 1966). The chemical structure of rifampicin is C43H58N4O12 and its molecular weight is 822.95; its molecular structure is shown in Figure 126.1. Additional semisynthetic rifamycins in clinical use include rifabutin (see Chapter 127, Rifabutin), rifapentine (see Chapter 129, Rifapentine), and rifaximin (see Chapter 128, Rifaximin).
Bacteria and fungi as major bio-sources to fabricate silver nanoparticles with antibacterial activities
Published in Expert Review of Anti-infective Therapy, 2022
Also, there are several fungi and bacteria sources having natural antibiotics metabolites. In the case of fungi, griseofulvin and cephalosporin antibiotics produced by the mycelium of Penicillium griseofulvum and Acremonium chrysogenum, respectively [20]. In the case of bacteria, Streptomyces hygroscopicus, Saccharopolyspora erythraea related to Actinomycete, Streptomyces griseus, Streptomyces aureofaciens, and Amycolatopsis orientalis are used to produce geldanamycin, erythromycin, streptomycin, tetracycline, and vancomycin antibiotics, respectively [21,22]. It is worth noting that the phylum Actinobacteria specifically the genus Streptomyces can produce ~80% of the most antibiotics [23]. Physicochemical properties and chemical structures of important secondary metabolites extracted from bacteria and fungi are presented in Table 1, respectively.
Formaldehyde as an alternative to antibiotics for treatment of refractory impetigo and other infectious skin diseases
Published in Expert Review of Anti-infective Therapy, 2019
Philip Nikolic, Poonam Mudgil, John Whitehall
In addition to its wide use in manufacturing and as a preservative, formaldehyde is also an important cellular metabolite in the metabolism of methylated compounds in methylotrophic bacteria. It is generally produced by methanotrophic and methylotrophic bacteria during oxidation of hydrocarbons such as methane and methanol [10]. As a result, bacteria have developed methods to tolerate the toxic effects of formaldehyde. This has been primarily through the enzymatic breakdown of formaldehyde into less toxic products. One such method is found in Amycolatopsis methanolica and Mycobacterium gastri in the form of a formaldehyde dismutase that breaks formaldehyde down into formate and methanol. However, both species are still susceptible to formaldehyde at concentrations above 0.8 mM [39].
Anti-hyperglycemic and genotoxic studies of 1-O-methyl chrysophanol, a new anthraquinone isolated from Amycolatopsis thermoflava strain SFMA-103
Published in Drug and Chemical Toxicology, 2021
Cheemalamarri Chandrasekhar, Hemshikha Rajpurohit, Kalpana Javaji, Madhusudana Kuncha, Aravind Setti, A. Zehra Ali, Ashok K. Tiwari, Sunil Misra, C. Ganesh Kumar
In the present study, OMC from a rare actinomycete, Amycolatopsis thermoflava strain SFMA-103 (MTCC 25037) (Kumar et al.2017) was evaluated for its potential anti-diabetic properties based on in silico studies followed by in vitro studies against α-amylase and α-glucosidase with respect to acarbose as a standard. The efficacy of OMC against type II diabetes was further tested in starch-loaded Wistar rat model. To determine its safety and possible therapeutic usage, a detailed genotoxic assessment was carried out in both in vitro (CHO cell line) and in vivo (Swiss albino mice) models.