Coenzyme A, transhydrogenase and

A new avenue of investigation was opened when it was observed that 17j8-estradiol stimulates NAD reduction in the presence of human placenta homogenates and isocitrate. This was a puzzling observation because most of the isocitrate dehydrogenase found in a soluble fraction requires NADP as a coenzyme. Williams and Ashman demonstrated that the stimulation of NAD reduction resulted from an effect of the steroid on a transhydrogenase, which would catalyze... 

In discussion of nomenclature of malic acid decomposing enzymes, mention should be made of malate-lactate transhydrogenase. This enzyme, isolated from Micrococcus lactiyticus (VielloneUa alcalescens), a bacterium found in vertibrates, can catalyze reversibly the conversion of L-malic and pyruvic acids to L-lactic and oxaloacetic acids with NAD as coenzyme (36). 

Transhydrogenase. DPN and TPN are equivalent in terms of their ability to oxidize (or reduce) other molecules, since precisely the same structure is involved in each nucleotide. The possibility of a reaction equilibrating the two coenzymes by transferring hydrogen from one to the other had been considered for many years, and finally was found... 

Another mechanism for the interconversion of the pyridine nucleotides involves the enzyme pyridine nucleotide transhydrogenase, which has been purified from extracts of Pseudomonas jiuorescens. - It catalyzes a number of reactions, of which two are given below. (The reduced coenzymes are represented as TPNH and DPNH.)... 

---