Quantitative high-performance liquid chromatographic analysis of branched-chain 2-keto acids in biological samples

Cloning and characterization of a novel 2-ketoisovalerate reductase from the beauvericin producer Fusarium proliferatum LF061

Background

The ketoisovalerate reductase (EC 1.2.7.7 ) is required for the formation of beauvericin via the nonribosomal peptide synthetase biosynthetic pathway. It catalyzes the NADPH-specific reduction of ketoisovaleric acid to hydroxyisovalerate. However, little is known about the bioinformatics’ data about the 2-Kiv reductase in Fusarium. To date, heterologous production of the gene KivRFp from Fusarium has not been achieved.

Results

The KivRFp gene was subcloned and expressed in Escherichia coli BL21 using the pET expression system. The gene KivRFp contained a 1,359 bp open reading frame (ORF) encoding a polypeptide of 452 amino acids with a molecular mass of 52 kDa. Sequence analysis indicated that it showed 61% and 52% amino acid identities to ketoisovalerate reductase from Beauveria bassiana ATCC 7159 (ACI30654) and Metarhizium acridum CQMa 102 (EFY89891), respectively; and several conserved regions were identified, including the putative nucleotide-binding signature site, GXGXXG, a catalytic triad (Glu405, Asn184, and Lys285). The KivRFp exhibited the highest activity at 35°C and pH 7.5 respectively, by reduction of ketoisovalerate. It also exhibited the high level of stability over wide temperature and pH spectra and in the presence of metal ions or detergents.

Conclusions

A new ketoisovalerate reductase KivRFp was identified and characterized from the depsipeptide-producing fungus F. proliferatum. KivRFp has been shown to have useful properties, such as moderate thermal stability and broad pH optima, and may serve as the starting points for future protein engineering and directed evolution, towards the goal of developing efficient enzyme for downstream biotechnological applications.

High-performance liquid chromatographic measurement of leucine and alpha-ketoisocaproate in whole blood: application to fetal protein metabolism

Evaluation of fetal protein metabolism requires measurement of a number of variables including umbilical blood flow, CO2 radioactivity, as well as plasma specific activities, whole blood concentration, and radioactivity of leucine and alpha-ketoisocaproate. This report details methods of analysis for whole blood concentration and radioactivity of leucine and alpha-ketoisocaproate using high-performance liquid chromatography that can be done on minimal blood volumes and are sufficiently accurate to detect the small arteriovenous differences important in measurements of fetal metabolism. Using these methods, the important components of fetal protein metabolism such as protein synthesis can be calculated with sufficient accuracy to detect differences as small as 10% provided appropriate experimental designs are used.