SUBNIT COMPOSITION OF HORSE LIVER ALCOHOL DEHYDROGENASE

Horse liver alcohol dehydrogenase, LADH, occurs in multiple, electrophoretically separable forms. The subunit composition of the three main forms is described in this paper. The enzyme LADHe (EE) consists of two identical halves (E, for activity with ethanol). The enzyme LADHss (SS) consists of two other identical halves (S, for activity also on steroids). The electrophoretically intermediate form LADHs (ES) is a hybrid consisting of one subunit E and one subunit S. Various conditions of dissociation and reconstitution of ES are investigated. Although in some of these conditions the relative amounts of the isoenzymes reconstituted are variable, formation of only three isoenzymes is observed. The results suggest that the quaternary structure of LADH is dimeric. The basis for the use of E and S in the nomenclature of the other isoenzymes of LADH is discussed. © 1969.