Artefactual pyruvate and 2-oxobutyrate produced by trimethylsilylation of methylmalonic and ethylmalonic acids in the presence of oxygen
Trimethylsilylation of methylmalonic and ethylmalonic acids in the presence of headspace atmospheric oxygen is shown to produce the trimethylsilyl derivatives of pyruvic and 2-oxobutyric acids, along with 2-hydroxy-2-methylmalonic and 2-hydroxy-2-ethylmalonic acids, respectively. This may lead to overestimation of these keto acids, if they were not oximated in the original sample, and the mistaken reporting of the 2-hydroxymalonates.
Experiment-originated variations, and multi-peak and multi-origination phenomena in derivatization-based GC-MS metabolomics
Gas chromatography combined with mass spectrometry (GC-MS), in particular derivatization-based GC-MS, is one of the most commonly used analytical methods in metabolomics. However, experiment-derived variations and originations of chromatographic peaks are two fundamental issues that could influence interpretation of metabolic pathways. Here, we focus on some pitfalls and limitations, especially the commonly ignored multi-origination and multi-peak phenomena in derivatization-based GC-MS metabolomics. We use examples to illustrate that ignoring these two factors could lead to wrong interpretations of results and serious metabolic implications. We also discuss strategies to overcome some of these confounding factors.
Metabolic diseases and mental retardation. II: The comparative effects of α-ketoisocaproic acid inhibition of pyruvate decarboxylation in chick. Liver and brain
1. 
1. The optimal conditions for pyruvate decarboxylation in 20-day-old chick liver and brain homogenates were determined. 
 
2. 
2. The apparent Km values for pyruvate were found to be 1.1 × 10−3M in liver and 2.0 × 10−3M in brain. 
 
3. 
3. Pyruvate decarboxylation was more active in brain than in liver as assayed. 
 
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4. Apparent Ki values of α-ketoisocaproic acid were found to be 5.0 × 10−3M in brain and 2.5 × 10−3M in liver. The type of inhibition was competitive in both cases. 
 
5. 
5. These kinetic parameters are comparable with other values quoted in the literature. 
 
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6. The use of the chick as a model in genetic diseases is discussed.