Tissue concentrations of conenzyme Q, ubichromenol and tocopherol in relation to protein status in the rat.

man & Villee, 1959; Jarabak, Adams, WilliamsAshman & Talalay, 1962). Talalay & WilliamsAshman (1958) suggested that a steroid dehydrogenase with dual nucleotide specificity is responsible for steroid-dependent transhydrogenation, with one site on the enzyme for which both nucleotides compete. At the stage of enzyme purification reached in the present work it has not been possible to separate NADor NADP-linked 3oc-hydroxy steroid-dehydrogenase activities from the transhydrogenase activity. It has been found, however, that ammonium sulphate stimulated the NADlinked dehydrogenase but not the NADP-linked dehydrogenase activity. Until the mechanism of 3oc-hydroxy steroiddependent transhydrogenation in rat liver is more fully explained by work with purer enzyme preparations, the role of anions in these reactions will be difficult to define.