Radical Glycyl

TABLE 6.10 Calculated and Experimental g Tensors (ppm) of Glycyl Radical in Solution (Water). The Experimental Data are Given With an Error of 400 ppm 

---

Leuthner B, C Leutwein, H Schulz, P Horth, W Haehnel, E Schiltz, H Schagger, J Heider (1998) Biochemical and genetic characterisation of benzylsuccinate synthase from Thauera aromatica a new glycyl-radical catalysing the first step in anaerobic toluene degradation. Mol Microbiol 28 515-628. 

Morasch B, HH Richnow, A Vieth, B Schink, RU Meckenstock (2004) Stable isotope fractionation caused by glycyl radical enzymes during bacterial degradation of aromatic compounds. Appl Environ Microbiol 70 2935-2940. 

The reaction energy for Eq. 5 amounts to -54.7 kj/mol at the ROMP2 level, indicating a substantial captodative stabilization for glycyl radical (9) even with this definition. 

The 2-glycyl radical H2NCHCO2H has been generated by collisional neutralization... 

The resulting glycyl radical couples with the oxygen radical that is bound to CuB (step e). 

Benzylsuccinate synthase has an amino acid sequence homologous to that of pyruvate formate lyase (p. 799 -801), contains a glycyl radical, and is activated in a manner similar to activation of pyruvate formate lyase. Propose a mechanism for formation of benzylsuccinate. See Krieger et al.383... 

It is thought that the activator becomes reduced by the excess electron of the Fe/ S cluster and then cleaves to produce a 5 -deoxyadenosyl radical, which in turn produces the glycyl radical [52], So the evidence of the redox-catalytic nature of the Fe/S cluster is not very strong, as there is no indication of direct coordination of the activator or its products to the cluster. 

Then, as case study, we consider the glycine and glycyl radicals (Fig. 6.2) in solution. As mentioned above, the calculation of magnetic tensors needs to take into account the several factors such as the geometries, environmental effects, and dynamical effects (vibrational averaging from intramolecular vibrations and/or solvent librations). We use an integrated computational approach where the molecular... 

FIGURE 6.2 Structures of glycine and glycyl radicals. The orientations of the principal axes of the g tensor are also shown. 

The performances of the PBEO and B3LYP/N07D models for a typical problem involving at the same time stereoelectronic, vibrational, and environmental effects can be judged by the results reported in Tables 6.7-6.10 for the glycine and glycyl ° radicals (Fig. 6.2) in aqueous solution. 

TABLE 6.8 Hyperfine Coupling Constants (in Gauss) of Glycyl Radical... 

The best-studied enzymes to date that contain glycyl radicals are pyruvate formate-lyase (PFL) and a ribonucleoside triphosphate reductase (ARR), both isolated from anaerobically growing E. coli. These enzymes play central roles in the anaerobic metabolism of the bacterium. The first catalyzes the reversible formation of acetyl-CoA and formate from pyruvate and coenzyme A, while the second is responsible for synthesizing the deoxyribonucleotide monomers of the polymer DNA. It is intriguing to note that formate, a product of the PFL reaction, is a substrate for the ARR. It supplies the reducing equivalents needed for each round of deoxynucleotide synthesis. ... 

---