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At least 829 records · Page 46Linked to original sources
PubMed1996

Sterol esterification in yeast: a two-gene process.

Unesterified sterol modulates the function of eukaryotic membranes. In human cells, sterol is esterified to a storage form by acyl-coenzyme A (CoA): cholesterol acyl transferase (ACAT). Here, two genes are identified, ARE1 and ARE2, that encode ACAT-related enzymes in yeast. The yeast enzymes are 49 percent identical to each other and exhibit 23 percent identity to human ACAT. Deletion of ARE2 reduced sterol ester levels to approximately 25 percent of normal levels, whereas disruption of ARE1 did not affect sterol ester biosynthesis. Deletion of both genes resulted in a viable cell with undetectable esterified sterol. Measurements of [14C]acetate incorporation into saponified lipids indicated down-regulation of sterol biosynthesis in the are1 are2 mutant cells. With the use of a consensus sequence to the yeast and human genes, an additional number of the ACAT gene family was identified in humans.

Acetates↗
PubMed2003

Tri16 is required for esterification of position C-8 during trichothecene mycotoxin production by Fusarium sporotrichioides.

We previously characterized Tri1, a gene required for hydroxylation of the C-8 position during trichothecene mycotoxin biosynthesis in Fusarium sporotrichioides NRRL 3299. Sequence analysis of the region surrounding Tri1 revealed a gene, named Tri16, which could encode an acyltransferase. Unlike the wild-type parent strain NRRL 3299, which accumulates primarily T-2 toxin along with low levels of diacetoxyscirpenol (DAS) and neosolaniol (NEO) and trace amounts of 8-propionyl-neosolaniol (P-NEO) and 8-isobutyryl-neosolaniol (B-NEO), mutants containing a disruption of Tri16 were blocked in the production of the three C-8 esterified compounds T-2 toxin, P-NEO, and B-NEO and accumulated the C-8-hydroxylated compound NEO along with secondary levels of DAS. These data indicate that Tri16 encodes an acyltransferase that catalyzes the formation of ester side groups at C-8 during trichothecene biosynthesis. We also report the presence of a Tri16 ortholog in Gibberella pulicaris R-6380 that is likely linked to a presumably inactive ortholog for Tri1.

Acyltransferases↗
PubMed2006

Cholesterol sensing, trafficking, and esterification.

Mammalian cells acquire cholesterol from low-density lipoprotein (LDL) and from endogenous biosynthesis. The roles of the Niemann-Pick type C1 protein in mediating the endosomal transport of LDL-derived cholesterol and endogenously synthesized cholesterol are discussed. Excess cellular cholesterol is converted to cholesteryl esters by the enzyme acyl-coenzyme A:cholesterol acyltransferase (ACAT) 1 or is removed from a cell by cellular cholesterol efflux at the plasma membrane. A close relationship between the ACAT substrate pool and the cholesterol efflux pool is proposed. Sterol-sensing domains (SSDs) are present in several membrane proteins, including NPC1, HMG-CoA reductase, and the SREBP cleavage-activating protein. The functions of SSDs are described. ACAT1 is an endoplasmic reticulum cholesterol sensor and contains a signature motif characteristic of the membrane-bound acyltransferase family. The nonvesicular cholesterol translocation processes involve the START domain proteins and the oxysterol binding protein-related proteins (ORPs). The properties of these proteins are summarized.

Amino Acid Sequence↗
PubMed1975

Cholesterol esterification and lipids in plasma and liver from newborn and young guinea pigs raised on milk and non-milk diet.

Plasma lecithin:cholesterol acyltransfer (LCAT), liver acyl-CoA:cholesterol acyltransfer (ACAT) and plasma and liver lipids were examined in newborn and young guinea pigs fed ordinary or a non-milk diet. LCAT in newborns was about 70% of the adult value, increased the first 3 days to values about three times the adult value, and decreased during the next 3 weeks to about adult value. Plasma lipids varied in a similar way. Liver ACAT in newborns was considerably higher than in adults. In young animals on non-milk diet the LCAT and ACAT were lower than in normally fed animals. LCAT was positively correlated to free cholesterol in plasma.

Acyltransferases↗
PubMed1986

Quantitative studies on the fetal lipid metabolism in rats: liver fatty acid esterification and conversion into carbon dioxide, and hepatic output of triglycerides and phospholipids into serum.

Fetal lipid metabolism was studied quantitatively using the 14C-1-palmitate in vivo tracer technique and compartment analysis, and in vitro incorporation experiments. The following conclusions can be drawn from our experiments. Fetal serum free fatty acids (FFA) exchange so rapidly with the FFA of another compartment that the FFA of both compartments can be considered as one homogeneous FFA compartment. The turnover time of this compartment was calculated to be 0.76 mumol FFA/min/l through this compartment. The incorporation of fetal serum FFAs into fetal liver triglyceride fatty acids (TG-FA) and phospholipid fatty acids (PL-FA) was calculated to be 0.05 and 0.14 mumol FFA/min/l, respectively. Thus, only 16% of the fetal serum FFA is incorporated into fetal liver lipids. The fetal serum TG-FA most likely originate in the fetal liver. The fetal liver puts out 0.025 mumol TG-FA/min/l and 0.10 mumol PL-FA/min/l into the fetal serum. The turnover times of fetal serum TG-FA and PL-FA are 100 and 39 min, respectively. The fetal liver conversion rate of fatty acids (FA) into CO2 determined in vitro (0.06 mumol FA/min/l) amounts to about 25% of the rate seen in the whole rat fetus.

Animals↗
PubMedDate not supplied

Partially reassembled high density lipoproteins. Effects on cholesterol flux, synthesis, and esterification in normal human skin fibroblasts.

The effects of a partially reassembled high density lipoprotein (PR-HDL) prepared by a detergent removal method on the cholesterol metabolism of fibroblasts has been tested under conditions of lipid depletion. The PR-HDL were composed of apolipoprotein A-I (1 mol) from human plasma HDL, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) 100 mol, and varying amounts of cholesterol. Below 15 mol%, the PR-HDL effected a net efflux of cholesterol from the fibroblasts; as a consequence, the activities of 3-hydroxy-3-methylglutaryl coenzyme A reductase and acyl coenzyme A acyltransferase, respectively, were increased and decreased. Above 15 mol% cholesterol in the PR-HDL, net influx of cholesterol was observed and 3-hydroxy-3-methyl-glutaryl coenzyme A reductase activity was decreased, while acyl coenzyme A acyltransferase activity was increased. The uptake of several phosphatidylcholines, apo A-I, and cholesterol were measured as a function of time. The rates of lipid transfer to the cells decreased with increasing hydrophobicity of the transferring lipid. By contrast, in parallel experiments a relatively small quantity of 125I apo A-I was associated with the cells. Our results suggest that a component of lipid transfer from PR-HDL to fibroblasts occurs via monomeric transfer through the aqueous phase that is independent of apo A-I binding.

Cells, Cultured↗