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G Gil

Publications and source records attributed to G Gil.

47 records · Page 3Linked to original sources
PubMed1982

Inactivation and reactivation of rat liver 3-hydroxy-3-methylglutaryl-CoA-reductase phosphatases: effect of phosphate, pyrophosphate and divalent cations.

Incubation of four purified rat liver HMG-CoA-reductase phosphatases (Gil, G., Sitges, M. and Hegardt, F.G. (1981) Biochim. Biophys. Acta 663, 211-221) with Mn2 or Mg2 caused a concentration-dependent activation of enzyme activities. The maximum effect for Mn2 was at 5 mM for all phosphatases. Fe2 caused inactivation only in reductase phosphatases IIa and IIb. Ca2 10 mM showed a slight effect of inactivation. Phosphate, pyrophosphate and adenine nucleotides inhibited the four reductase phosphatases, this process being concentration-dependent. cAMP did not inhibit the four phosphatases at all in the range of 0.01-8 mM. Preincubation of reductase phosphatases with PPi and subsequent dilution did not diminish the inactivation effect, showing that this ion inhibits the enzyme prior to the binding to the substrate. Phosphorylated sugars, but not free sugar, inactivated the four reductase phosphatases. PPi-inactivated enzymes were reactivated by Mg2 or Mn2, this process being time-dependent. The four phosphatases had different patterns of reactivation. Phosphatases Ib and IIb (low-molecular mass forms) were shown to be different enzymes as judged by: their divergent behaviour when inhibited with Fe2; their PPi response; kinetics of reactivation by Mg2 or Mn2 or PPi-inactivated enzymes; and thermal stability. A metalloenzyme character is suggested for reductase phosphatases.

Adenine Nucleotides↗
PubMed1981

Purification and properties of rat liver hydroxymethylglutaryl coenzyme A reductase phosphatases.

A procedure for the isolation and purification of two rat liver hydroxymethylglutaryl coenzyme A reductase phosphatases is described for the first time. Each of the preparations was obtained in two molecular forms of different molecular weights. The molecular weights of the holoenzymes were 480,000 and 310,000, respectively, while the molecular forms obtained after an ethanol treatment were in both cases 35,000. Several kinetic measurements were made which showed that the protein of Mr 35,000 was identical in both cases, irrespective of the holoenzymatic starting preparation used. The optimum pH of the three phosphatases ranged between 6.0 and 6.5. The Km of the phosphatases ranged between 6.5 and 19.5 nM when hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase was the substrate. The three HMG-CoA reductase phosphatases, upon incubation, released 32P from 32P-labelled HMG-CoA reductase. This dephosphorylation also produces an activation of the HMG-CoA reductase activity.

Animals↗
PubMedDate not supplied

Nucleotide sequence of 3-hydroxy-3-methyl-glutaryl coenzyme A reductase, a glycoprotein of endoplasmic reticulum.

The nucleotide sequence of a 4.8-kilobase mRNA for hamster 3-hydroxy-3-methylglutaryl coenzyme A reductase, the endoplasmic reticulum enzyme that controls cholesterol biosynthesis, shows that it is a protein of 887 amino acids (molecular weight 97,092) which contains three potential sites for asparagine-linked glycosylation. The reductase is a transmembrane glycoprotein, but in contrast to many other transmembrane glycoproteins, it lacks a cleavable or hydrophobic NH2-terminal signal sequence.

Amino Acid Sequence↗