ISOLATION AND CHARACTERIZATION OF 3 ALCOHOL-DEHYDROGENASE ISOZYMES FROM SYRIAN GOLDEN-HAMSTERS

Electrophoresis of freshly prepared tissue homogenates of the Syrian g olden hamster (Mesocricetus auratus) on starch gel followed by activit y staining with ethanol as the substrate revealed three major alcohol dehydrogenase (ADH) isozymes. One of these isozymes, TT-ADH, found onl y in the testes of golden hamsters was previously purified and partial ly characterized (Keung WM:Biochem. Biophys. Res. Commun. 156:38-45, 1 988). The other two, AA- and BB-ADH, which are most abundant in the li ver, have now been purified by affinity chromatography on (N-(6-aminoc aproyl)amino)propyl)pyrazole-sepharose and testosterone-17 beta-hemisu ccinate-agarose. Hamster AA-, BB-, and TT:ADH are all homodimers of mo lecular weight near 80,000 and each contains 4 atoms of zinc. Amino ac id analyses show that BB-ADH is most closely related to the gamma-form of human class I ADH, whereas AA- and TT-ADH are most closely related to the beta-form of the human enzyme. BB-ADH is the only hamster ADH that is active toward sterols and sensitive to testosterone and isofla vone Inhibition. These results suggest that hamster BB- and human gamm a gamma-ADH also share similar catalytic properties. AA- and TT-ADH ar e neither active toward sterols nor sensitive to testosterone or isofl avone inhibition; thus, they are functionally different from the human alpha alpha- or gamma gamma-ADHs Compared with AA- and BB-ADH, TT-ADH exhibits much higher K-m values toward primary aliphatic alcohols and cyclohexanol. AA- and BB-ADH share similar substrate specificities to ward primary aliphatic alcohols. However, they exhibit different stere ospecificities for secondary alcohols. BB-ADH prefers the (R)-(-)-isom er of P-butanol, whereas AA-ADH prefers the (S)-(-)-isomer. These resu lts further demonstrate that catalytically, hamster BE- and AA-ADH bel ong to different subfamilies of class I ADH.