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Human branched-chain L-amino acid aminotransferase: Activity and subcellular localization in cultured skin fibroblasts

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Summary

Assay conditions for measurement of human skin fibroblast branched-chain L-amino acid aminotransferase activity were established and applied to studies on subcellular distribution and kinetic properties of the enzyme. Digitonin fractionation of cultured cells revealed that the aminotransferase activity was mainly (at least about 95%) associated with mitochondrial citrate synthase activity. As tested with L-leucine, activity of the enzyme against amino group acceptors (forward reaction) was in the order 2-oxoglutarate ⩾ branched-chain > straight-chain 2-oxo acids (C3-C8). With 4-methyl-2-oxopentanoate, activity against amino group donors (reverse reaction) was in the order L-glutamate ⩾ branched-chain > straight-chain (C2-C6) and other L-amino acids. The data suggest that, in human fibroblasts, isoenzyme type I resides within the mitochondrial space. Possible implications for the metabolism of branched-chain compounds are discussed.

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Authors and Affiliations

  1. Institut für Physiologische Chemie II, Heinrich-Heine-Universität Düsseldorf, Auf'm Hennekamp 65, D-40225, Düsseldorf, Germany

    P. Schadewaldt

  2. Diabetes Forschungsinstitut, Klinische Biochemie, Heinrich-Heine-Universität Düsseldorf, Auf'm Hennekamp 65, D-40225, Düsseldorf, Germany

    P. Schadewaldt

  3. Kinderklinik, Heinrich-Heine-Universität Düsseldorf, Auf'm Hennekamp 65, D-40225, Düsseldorf, Germany

    U. Wendel & H. -W. Hammen

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  1. P. Schadewaldt
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  2. U. Wendel
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  3. H. -W. Hammen
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Schadewaldt, P., Wendel, U. & Hammen, H.W. Human branched-chain L-amino acid aminotransferase: Activity and subcellular localization in cultured skin fibroblasts. Amino Acids 9, 147–160 (1995). https://doi.org/10.1007/BF00805836

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