Enzyme variants

It has been shown that an AAC enzyme variant (AAC (6 )-Ib-cr, cr for ciprofloxacin resistance) found in various Enterobacteriaceae is capable of A-acetylating fluoroquinolones with an unmodified piperazinyl substituent at the amino nitrogen. Although the increase in MIC is low, this plasmid encoded quinolone resistance determinant can augment further development of clinically relevant resistance. 

The multiple human variants of G-6-PD and the relationship of their kinetic properties to the presence of hemolytic anemia under conditions which closely simulate the erythrocyte internal environment have been elegantly studied by Yoshida (112). This author found that those enzyme variants with significantly reduced physiological activity are those associated with hemolytic anemia. 

The CSN3 subunit interacts with IKKy, a component of the IsrB-kinase complex controlling NF-kB activity [32]. Additionally, it is the binding site for the CSN-associated kinases CK2 and PKD [31]. The subunit of the translation-initiation factor 3 complex, Int6/eIF3e, and the ubiquitin-conjugating enzyme variant, COPIO, have been identified as other cellular interactors [33, 34]. Also the HIV-1 Tat protein interacts with CSN 3 (our unpublished data). 

Arabidopsis COPIO is a ubiquitin-conjugating enzyme variant that acts together with COPl and the COP9 signalosome in repressing photomorphogenesis. Genes Dev. 2002, 36, 554-559. 

Each sample was mixed with the ionic liquid matrix (2,5-dihydroxybenzoic acid/pyridine) containing C-labelled glucose as internal standard and spotted on the target. MALDI-MS analysis generated reaction profiles by the simultaneous determination of product and substrate concentrations for each enzyme variant. The reaction profiles could be used to sort the enzyme variants into five different classes. 

The number of enzyme variants N at the theoretically maximum degree of diversity is given by the algorithm shown as ... 

Differentiation of the experimental concentration-time curve would then need interpolation or smoothing, e.g.,by using splines. Parallelization in a typical robotic environment is easy when using the integral method with a few or even only one single well for characterization of one enzyme variant. 

Biosciences, Uppsala, Sweden). The purification was performed as described elsewhere [11]. Finally, the purified enzyme variants were lyophilized and stored at -20 C. 

In order to increase the understanding of ThDP-dependent enzymes, the identification of amino acid side chains important for the catalysis of the carboligase reaction in pyruvate decarboxylase from Zymomonas mohilis (E.C. 4.1.1.1) and benzoylformate decarboxylase from Pseudomonasputida (E.C. 4.1.1.7) was a major task. Using site-directed mutagenesis and directed evolution, various enzyme variants were obtained, differing in substrate specificity and enantioselectivity. 

Recently, the U S. Food and Drug Administration approved the Amplichip, the first DNA microrarray application in clinic (12) to help physicians to test the dosage of drugs that are differently metabolized by cytochrome P450 enzyme variants. 

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