Portal de Periódicos da CAPES

Mitochondrial autonomy Studies on the mitochondral glycoprotein: Glucosyl and mitochondrial glycoprotein: Mannosyl transferase enzyme systems of rat liver mitochondria utilizing endogenous acceptors

1971; Elsevier BV; Volume: 230; Issue: 2 Linguagem: Inglês

10.1016/0304-4165(71)90228-5

1872-8006

Sarah S. Martin, H.Bruce Bosmann,

ATP Synthase and ATPases Research

Glycoprotein and protein synthesis by isolated rat liver mitochodria was measured by the incorporation of radioactivity labeled monosaccharides or leucine into mitochodrial proteins. The transfer from the following nucleoside diphosphate-[14C]monosaccharide precursors onto endogenous mitochondrial acceptors was demonstrated: UDP-glucose, GDP-mannose, UDP-galactose, GDP-fucose, UDP-N-acetylglucosamine and UDP-N-acetylgalactosamine. In particular the enzyme systems involved in the transfer from UDP-glucose (mitochodrial glycoprotein: glycosyl transferase system) and GDP-mannose (mitochondrial glycoprotein: mannosyl transferase system) were studied in detail. Activity of these transferase systems was dependent on structural intactness of the mitochondrion, not very dependent on an external energy source, and absolutely dependent on divalent cations for activation. For the mitochondrial glycoprotein: glycosyl and mitochondrial glycoprotein: mannosyl transferase systems Ca2+ and Mg2+ were the best activators of ten cations tested. The catalytic activity of the mitochondrial glycoprtein: glucosyl transferase system had a sharp pH dependence with the maximum at pH 7, while the mitochondrial glycoprotein: mannosyl transferase system had a broad pH dependence with the maximum between pH 8.0 and 9.2. Both transferase systems had an optimum catalytic activity at a temperature of 35°. Chloramphenicol (1.0 mg/ml) inhibited protein synthesis in isolated mitochondria 75% but had no effect on glycosyllation, and cycloheximide (1.0 mg/ml) had no effect on either protein synthesis or glycosyllation. Glycoproteins synthesized in vitro by mitochondria were demonstrated to be located mainly in the inner mitochondrial membrane, and the transferases and endogenous acceptor proteins were also shown to be localized there.