Pyruvate oxidase, catalytic reactions

Several aaRS-like proteins are involved in metabobc pathways (1). For example, E. coli asparagine synthase, an aspartyl-tRNA synthetase (AspRS)-like enzyme, catalyzes the synthesis of asparagine from aspartate and ATP. A paralog of LysRS-II, called PoxA/GenX, is important for pyruvate oxidase activity in E. coli and Salmonella typhimurium and for virulence in S. typhimurium. The E. coli biotin synthetase/repressor protein (BirA), which has a domain that resembles structurally the seryl-tRNA synthetase (SerRS) catalytic domain, activates biotin to modify posttranslationaUy various metabolic proteins involved in carboxylation and decarboxylation. BirA can also bind DNA and regulate its own transcription using biotin as a corepressor. A histidyl-tRNA synthetase (HisRS)-hke protein from Lactococcus lactis, HisZ is involved in the allosteric activation of the phosphoribosyl-transferase reaction. 

We have in the present chapter shown results from theoretical model system studies of the catalytic reaction mechanisms of three radical enzymes Galatose oxidase. Pyruvate formate-lyase and Ribonucleotide reductase. It is concluded that small models of the key parts of the active sites in combination with the DPT hybrid functional B3LYP and large basis sets provides a good description of the catalytic machineries, with low barriers for the rate determining steps and moderate overall exothermicity. The models employed are furthermore able to reproduce all the observed features in terms of spin distributions and reactive intermediates. 

Figure 1. Catalytic reactions of pyruvate oxidase (Path ) and acetolactate synthase (Path...

Even more impressive is Diederich s pyruvate oxidase mimic based on a cyclophane (Fig. 4) in methanol this host can bind an aromatic aldehyde within its cavity, create a covalent intermediate by reaction with its attached thiazolium group, oxidise this tethered intermediate by intramolecular transfer of a hydride-equivalent to the appended flavin, and then release the methyl ester product by solvolysis. Catalytic... 

Several flow strategies involving enzymatic reactions have been applied for determination of LA in food and beverages. Most of the work to be explored in this chapter involves the catalytic action of lactate dehydrogenase (LDFl) and lactate oxidase (LOD) in the conversion of LA into pyruvic acid (Figure 12.2). LDH requires a biological redox... 

---