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Purification of a new dihydrolipoamide dehydrogenase from Escherichia coli.

Institut Jacques Monod, Paris, France.

ABSTRACT

I purified a new dihydrolipoamide dehydrogenase from a lpd mutant of Escherichia coli deficient in the lipoamide dehydrogenase (EC 1.6.4.3) common to the pyruvate dehydrogenase (EC 1.2.4.1) and 2-oxoglutarate dehydrogenase complexes. The occurrence of the new lipoamide dehydrogenase in lpd mutants, including a lpd deletion mutant and the immunological properties of the enzyme, showed that it is different from the lpd gene product. The new dihydrolipoamide dehydrogenase had a molecular weight of 46,000, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It was expressed in low amounts. It catalyzed the NAD+-dependent reduction of dihydrolipoamide with a maximal activity of 20 mumol/min per mg of protein and exhibited a hyperbolic dependence of catalytic activity on the concentration of both dihydrolipoamide and NAD+. The possible implication of the new dihydrolipoamide in the function of 2-oxo acid dehydrogenase complexes is discussed, as is its relation to binding protein-dependent transport.

This article has been cited by other articles:

• Hakansson, A. P., Smith, A. W. (2007). Enzymatic Characterization of Dihydrolipoamide Dehydrogenase from Streptococcus pneumoniae Harboring Its Own Substrate. J. Biol. Chem. 282: 29521-29530 [Abstract] [Full Text]