BB-Specific Transhydrogenases

Nicotinamide nucleotide transhydrogenases may be divided into two classes. One class is present in certain bacteria, and possibly in some plants, is an easily extractable, water-soluble enzyme is not functionally linked to the energy-transfer system of the bacterial membrane is a flavoprotein and is specific for the 4B-hydrogen atom of both NADH and NADPH. The other class is present in both certain bacteria and in mitochondria is a firmly membrane-bound water-insoluble enzyme is functionally linked to the energy-transfer system of the bacterial or mitochondrial membrane is not known to be a flavoprotein and is specific for the 4A-hydrogen atom of NADH and the 4B-hydrogen atom of NADPH. For the sake of convenience, the two classes of enzyme will be referred to below as BB-specific and AB-specific transhydrogenases, respectively. [Pg.52]

The kinetic properties (see Section II,E) and spectral characteristics (7, 9, 10, 17, 19) of the BB-specific transhydrogenases strongly suggest that these enzymes are fiavoproteins. Consistent with this suggestion, Louie and Kaplan (7) showed that, in the presence of 1 M urea, was taken up from the medium and was incorporated into the reduced nicotinamide nucleotide. Direct proof for the occurrence of FAD in both the... [Pg.57]

Assay of AB-specific transhydrogenase is principally identical to that of BB-specific transhydrogenase (see Section II,C) i.e., with the natural nicotinamide nucleotides, an enzymic regenerating system is used to keep the concentration of one of the substrates constant (30, SB, 66-68, 66)... [Pg.68]

Preparations op BB-Specific Transhydrogenase from Various Sources... [Pg.56]

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