Characteristics of insulin resistant (IR) vs. moderately insulin sensitive (MIS) veal calves.

<p>Characteristics of insulin resistant (IR) vs. moderately insulin sensitive (MIS) veal calves.</p

Marker metabolites of insulin resistance found in OPLS-DA models of HILIC and C18 LC-MS plasma metabolic profiling of veal calves.

<p>Marker metabolites of insulin resistance found in OPLS-DA models of HILIC and C18 LC-MS plasma metabolic profiling of veal calves.</p

Metabolic pathway analysis of the putative identified marker metabolites of insulin resistance (Table 1) found in blood plasma of veal calves.

<p>Metabolic pathway analysis of the putative identified marker metabolites of insulin resistance (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0179612#pone.0179612.t001" target="_blank">Table 1</a>) found in blood plasma of veal calves.</p

Functional and Structural Characterization of an Unusual Cofactor-Independent Oxygenase

The vast majority of characterized oxygenases use bound cofactors to activate molecular oxygen to carry out oxidation chemistry. Here, we show that an enzyme of unknown activity, RhCC from Rhodococcus jostii RHA1, functions as an oxygenase, using 4-hydroxy­phenyl­enol­pyruvate as a substrate. This unique and complex reaction yields 3-hydroxy-3-(4-hydroxy­phenyl)-pyruvate, 4-hydroxy­benzaldehyde, and oxalic acid as major products. Incubations with H₂¹⁸O, ¹⁸O₂, and a substrate analogue suggest that this enzymatic oxygenation reaction likely involves a peroxide anion intermediate. Analysis of sequence similarity and the crystal structure of RhCC (solved at 1.78 Å resolution) reveal that this enzyme belongs to the tautomerase superfamily. Members of this superfamily typically catalyze tautomerization, dehalogenation, or decarboxylation reactions rather than oxygenation reactions. The structure shows the absence of cofactors, establishing RhCC as a rare example of a redox-metal- and coenzyme-free oxygenase. This sets the stage to study the mechanistic details of cofactor-independent oxygen activation in the unusual context of the tautomerase superfamily