title: Properties of hexosaminidases in cell-free extracts of rainbow trout livers and effects of thyroid hormones.
abstract: 1. The kinetic and physical properties of hexosaminidase (EC 3.2.1.30) activity were studied in liver extracts of juvenile rainbow trout. 2. Differential centrifugation studies failed to unequivocally demonstrate the sub-cellular localization of hexosaminidase, but indicated that the hexosaminidase activity was associated with the mitochondrial and lysosomal fractions. 3. Cell-free, Triton X-100 liver extracts indicated a pH optimum and activation energies comparable to those of mammals, but for other properties trout hepatic hexosaminidase differed markedly from its mammalian counterpart. 4. In contrast to the situation in rats, trout hexosaminidase was uninfluenced by a wide range of T4 and T3 doses administered by either injection or immersion routes. 5. T4 administration increased plasma T4 with minor change in plasma T3, indicating inhibition of T4 to T3 conversion by high T4 levels.
mesh_terms: D000118:Acetylglucosaminidase / Q000378:metabolism*; D000818:Animals; D002474:Cell-Free System; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D006596:Hexosaminidases / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D051381:Rats; D012487:Salmonidae / Q000378:metabolism*; D013974:Thyroxine / Q000097:blood / Q000494:pharmacology*; D014284:Triiodothyronine / Q000097:blood / Q000494:pharmacology*; D014337:Trout / Q000378:metabolism*
chemical_list: D014284:Triiodothyronine; D006596:Hexosaminidases; D000118:Acetylglucosaminidase; D013974:Thyroxine