Answers are grounded in this paper and cite their sources.
The capacity of acyl-CoA:cholesterol O-acyltransferase (ACAT) 2 to differentiate cholesterol from the plant sterol, sitosterol, was compared with that of the sterol esterifying enzymes, ACAT1 and lecithin:cholesterol acyltransferase (LCAT). Cholesterol-loaded microsomes from transfected cells containing either ACAT1 or ACAT2 exhibited significantly more ACAT activity than their sitosterol-loaded counterparts. In sitosterol-loaded microsomes, both ACAT1 and ACAT2 were able to esterify sitosterol albeit with lower efficiencies than cholesterol. The mass ratios of cholesterol ester to sitosterol ester formed by ACAT1 and ACAT2 were 1.6 and 7.2, respectively. Compared with ACAT1, ACAT2 selectively esterified cholesterol even when sitosterol was loaded into the microsomes. To further characterize the difference in sterol specificity, ACAT1 and ACAT2 were compared in intact cells loaded with either cholesterol or sitosterol. Despite a lower level of ACAT activity, the ACAT1-expressing cells esterified 4-fold more sitosterol than the ACAT2 cells. The data showed that compared with ACAT1, ACAT2 displayed significantly greater selectively for cholesterol compared with sitosterol. The plasma cholesterol esterification enzyme lecithin:cholesterol acyltransferase was also compared. With recombinant high density lipoprotein particles, the esterification rate of cholesterol by LCAT was only 15% greater than for sitosterol. Thus, LCAT was able to efficiently esterify both cholesterol and sitosterol. In contrast, ACAT2 demonstrated a strong preference for cholesterol rather than sitosterol. This sterol selectivity by ACAT2 may reflect a role in the sorting of dietary sterols during their absorption by the intestine in vivo. The capacity of acyl-CoA:cholesterol O-acyltransferase (ACAT) 2 to differentiate cholesterol from the plant sterol, sitosterol, was compared with that of the sterol esterifying enzymes, ACAT1 and lecithin:cholesterol acyltransferase (LCAT). Cholesterol-loaded microsomes from transfected cells containing either ACAT1 or ACAT2 exhibited significantly more ACAT activity than their sitosterol-loaded counterparts. In sitosterol-loaded microsomes, both ACAT1 and ACAT2 were able to esterify sitosterol albeit with lower efficiencies than cholesterol. The mass ratios of cholesterol ester to sitosterol ester formed by ACAT1 and ACAT2 were 1.6 and 7.2, respectively. Compared with ACAT1, ACAT2 selectively esterified cholesterol even when sitosterol was loaded into the microsomes. To further characterize the difference in sterol specificity, ACAT1 and ACAT2 were compared in intact cells loaded with either cholesterol or sitosterol. Despite a lower level of ACAT activity, the ACAT1-expressing cells esterified 4-fold more sitosterol than the ACAT2 cells. The data showed that compared with ACAT1, ACAT2 displayed significantly greater selectively for cholesterol compared with sitosterol. The plasma cholesterol esterification enzyme lecithin:cholesterol acyltransferase was also compared. With recombinant high density lipoprotein particles, the esterification rate of cholesterol by LCAT was only 15% greater than for sitosterol. Thus, LCAT was able to efficiently esterify both cholesterol and sitosterol. In contrast, ACAT2 demonstrated a strong preference for cholesterol rather than sitosterol. This sterol selectivity by ACAT2 may reflect a role in the sorting of dietary sterols during their absorption by the intestine in vivo. On an average day, humans will consume 300–500 mg of dietary cholesterol and through the action of the small intestine will absorb 40–50% of this sterol (1Wilson M.D. Rudel L.L. J. Lipid Res. 1994; 35: 943-955Abstract Full Text PDF PubMed Google Scholar). In addition to cholesterol, 250–500 mg of plant and shellfish-derived sterols can be ingested daily and, depending upon their chemical structure, will be differentially absorbed by the intestine (2Heinemann T. Axtmann G. von Bergmann K. Eur. J. Clin. Invest. 1993; 23: 827-831Crossref PubMed Scopus (353) Google Scholar, 3Salen G. Ahrens Jr., E.H. Grundy S.M. J. Clin. Invest. 1970; 49: 952-967Crossref PubMed Scopus (386) Google Scholar, 4Connor W.E. Lin D.S. Gastroenterology. 1981; 81: 276-284Abstract Full Text PDF PubMed Scopus (15) Google Scholar, 5Gregg R.E. Connor W.E. Lin D.S. Brewer Jr., H.B. J. Clin. Invest. 1986; 77: 1864-1872Crossref PubMed Scopus (96) Google Scholar). The most abundant of the dietary non-cholesterol sterols is sitosterol, which comes from plant and vegetable products. Even though sitosterol only differs from cholesterol by the presence of an ethyl group at the C-24 position of the side chain, the intestine will absorb only 5% of the sitosterol consumed on a daily basis (2Heinemann T. Axtmann G. von Bergmann K. Eur. J. Clin. Invest. 1993; 23: 827-831Crossref PubMed Scopus (353) Google Scholar, 3Salen G. Ahrens Jr., E.H. Grundy S.M. J. Clin. Invest. 1970; 49: 952-967Crossref PubMed Scopus (386) Google Scholar). The factor(s) determining the differential absorption of cholesterol and sitosterol in intestinal enterocytes is not identified. The ATP binding cassette transporters, ABCG5 and ABCG8, are one set of proteins that are essential in intestinal sterol sorting and absorption. Loss of function mutations in both alleles encoding either ABCG5 or ABCG8 results in sitosterolemia, a disorder in which sitosterol and all other dietary sterols are hyperabsorbed (6Berge K.E. Tian H. Graf G.A. Yu L. Grishin N.V. Schultz J. Kwiterovich P. Shan B. Barnes R. Hobbs H.H. Science. 2000; 290: 1771-1775Crossref PubMed Scopus (1361) Google Scholar, 7Lee M.H. Lu K. Hazard S. Yu H.W. Shulenin S. Hidaka H. Kojima H. Allikmets R. Sakuma N. Pegoraro R. Srivastava A.K. Salen G. Dean M. Patel S.B. Nat. Genet. 2001; 27: 79-83Crossref PubMed Scopus (0) Google Scholar). ABCG5 and ABCG8 are believed to form a heterodimer that localizes to the apical plasma membrane of the enterocyte (8Graf G.A. Li W.-P. Gerard R.D. Gelissen I. White A. Cohen J.C. Hobbs H.H. J. Clin. Invest. 2002; 110: 659-669Crossref PubMed Scopus (299) Google Scholar) to return plant and shellfish sterols back to the lumen of the intestine. Acyl-CoA:cholesterol O-acyltransferase 2 (ACAT2) 1The abbreviations used are: ACATacyl-CoA:cholesterol O-acyltransferaseLCATlecithin:cholesterol acyltransferaseHDLhigh density lipoproteinCDcyclodextrinFCfree cholesterolCEcholesteryl esterANOVAanalysis of variancePOPC3-sn-phosphatidylcholine, 2-oleoyl-1-palmitoyl. may be another protein that facilitates differential absorption of dietary sterols. ACAT2 is highly expressed in enterocytes where it functions to esterify cholesterol for packaging, as cholesteryl esters, into the neutral lipid core of nascent chylomicrons (9Lee R.G. Willingham M.C. Davis M.A. Skinner K.A. Rudel L.L. J. Lipid Res. 2000; 41: 1991-2001Abstract Full Text Full Text PDF PubMed Google Scholar, 10Buhman K.K. Accad M. Novak S. Choi R.S. Wong J.S. Hamilton R.L. Turley S. Farese Jr., R.V. Nat. Med. 2000; 6: 1341-1347Crossref PubMed Scopus (297) Google Scholar). ACAT2 may also aid in sorting dietary sterols in the enterocytes by discriminating among them as substrate candidates. Several in vivo studies (11Swell L. Trout Jr., E.C. Field Jr., H. Treadwell C.R. Proc. Soc. Exp. Biol. Med. 1959; : 140-142Crossref PubMed Scopus (5) Google Scholar, 12Bhattacharyya A.K. Lopez L.A. Biochim. Biophys. Acta. 1979; 574: 146-153Crossref PubMed Scopus (32) Google Scholar, 13Bhattacharyya A.K. Am. J. Physiol. 1981; 240: G50-G55PubMed Google Scholar, 14Field F.J. Mathur S.N. J. Lipid Res. 1983; 24: 409-417Abstract Full Text PDF PubMed Google Scholar, 15Ikeda I. Tanaka K. Sugano M. Vahouny G.V. Gallo L.L. J. Lipid Res. 1988; 29: 1583-1591Abstract Full Text PDF PubMed Google Scholar) have reported that a substantial amount of dietary free sitosterol can be internalized by enterocytes but that the vast majority of the sitosterol is not esterified and absorbed. In addition, in vitro studies using whole cells or isolated microsomes have indicated that sitosterol is poorly esterified by ACAT (14Field F.J. Mathur S.N. J. Lipid Res. 1983; 24: 409-417Abstract Full Text PDF PubMed Google Scholar, 16Tavani D.M. Nes W.R. Billheimer J.T. J. Lipid Res. 1982; 23: 774-781Abstract Full Text PDF PubMed Google Scholar, 17Field F.J. Born E. Mathur S.N. J. Lipid Res. 1997; 38: 348-360Abstract Full Text PDF PubMed Google Scholar). Therefore, because of its limited ability to esterify sitosterol, ACAT2 could not only limit the incorporation of sitosterol into chylomicrons but may also allow ABCG5 and ABCG8 to return the remaining free sitosterol back to the lumen of the intestine. acyl-CoA:cholesterol O-acyltransferase lecithin:cholesterol acyltransferase high density lipoprotein cyclodextrin free cholesterol cholesteryl ester analysis of variance 3-sn-phosphatidylcholine, 2-oleoyl-1-palmitoyl. However, in many of the previous studies, the expression of ABCG5 and ABCG8 in the experimental models should have limited, although to an unknown extent, the access of sitosterol to ACAT2. Moreover, several of the in vitro systems likely contained not only ACAT2 but also ACAT1. Therefore, in the current study, the ability of ACAT2 to esterify sitosterol was tested in AC29 cells expressing ACAT2 exclusively but not ABCG5 and ABCG8. AC29 cells expressing only ACAT1 were compared to ascertain whether ACAT1 and ACAT2 differ in their specificity toward sitosterol. Finally, it has been reported that 60–70% of the sitosterol in the plasma of patients with sitosterolemia is esterified (18Salen G. Kwiterovich Jr., P.O. Shefer S. Tint G.S. Horak I. Shore V. Dayal B. Horak E. J. Lipid Res. Full Text PDF PubMed Google Scholar, Eur. J. Clin. Invest. PubMed Scopus Google Scholar). The capacity of a cholesterol esterifying lecithin:cholesterol acyltransferase or to esterify sitosterol was using recombinant containing sitosterol or cholesterol. This enzyme is in and could to during used for the ACAT1 and ACAT2 cells were from the with 2 and and were from and respectively. of from ACAT1 and ACAT 2 cells transfected with ACAT1 or ACAT2 (9Lee R.G. Willingham M.C. Davis M.A. Skinner K.A. Rudel L.L. J. Lipid Res. 2000; 41: 1991-2001Abstract Full Text Full Text PDF PubMed Google Scholar) were into containing with 2 and and were in a 5% the cells were with from the and by at for at The cells were in ACAT with and were by The was at for at The was to a and was at for at in a the the was in ACAT with The was at of or in a was by in a containing of was either mg of free cholesterol or mg sitosterol To the of the sterol, the were at and In addition, the was to the were through a with a membrane and at in the the sterol of the cholesterol and sitosterol were to be and respectively. The ratios of to sterol for the cholesterol and sitosterol were and respectively. ACAT in with or in or in was in a The sterol was in and with ACAT containing This was into a containing either of ACAT1 or of ACAT2 microsomes. or was to the that the of the sterol was The for the ACAT1 and ACAT2 were and the of was was and was The containing the ACAT was for in a set at of the was and back into the for To the ACAT of was to the at for of was to the and the were to at at for the was from the and of the was and at The lipid was in containing free cholesterol and cholesteryl was to a and was using as the The were using and the and were from the into To the was of The free sterol was to to and the was for both ester and ester To the activity of the and in the microsomes, ACAT1 and ACAT2 microsomes were as the at the microsomes were to a and were at in a for at the the was with and was in The protein of the was by and the was by In addition, a was on the in the presence of of as an of the free sterol was by the on a at and in a with a using and a by ACAT1 or ACAT2 of or by ACAT1 or ACAT2 cells were into a containing A. On and were in to which were and respectively. On the and was to that the of the was 2 and the sterol was the to at for the was through a with a membrane The activity of the in the was by determining and the sterol by as In addition, on the ACAT1 and ACAT2 cells were to of the or at for or of was to containing the ACAT1 or ACAT2 respectively. at for 2 the cells were with with and by through a of was into a and the were and by as The protein of the was using a In addition, an of was in the presence of of The isolated lipid was for free sterol mass by as The lipid was and the sterol was by for sterol The difference free and sterol was by to the ester of or recombinant with a were as A. J. Biol. 1982; Full Text PDF PubMed Google Scholar). was used to recombinant with an into a was mg of and either mg of cholesterol or mg of sitosterol were in at In addition, of or of was to the the at the was with and its were for 2 To the was of and of which a of the it was with and in a for To the was of and of The was with and in a for The recombinant were of The protein of the was by and the sterol was using the To the of the recombinant a of containing of was with The with high proteins were on a a at for the were loaded the and at for and at for The was for with and the on the was using of LCAT of or an an LCAT was using LCAT and the recombinant J.S. A.K. M. K. and Scholar, A.K. J.S. J. Lipid Res. Full Text Full Text PDF PubMed Google Scholar). In one only the recombinant particles, of sterol was in In a both the and recombinant contained of and the amount of of cholesterol, and of of cholesterol, and of sitosterol. the were by either or with analysis by difference was at among the are by of by ACAT1 or ACAT2 in whether ACAT1 and ACAT2 differ in their ability to esterify sitosterol, AC29 cells expressing ACAT1 or ACAT2 were (9Lee R.G. Willingham M.C. Davis M.A. Skinner K.A. Rudel L.L. J. Lipid Res. 2000; 41: 1991-2001Abstract Full Text Full Text PDF PubMed Google Scholar). have ACAT protein expression or activity J. Biol. 1988; Full Text PDF PubMed Google Scholar, J. M.A. R.S. J. Biol. Full Text Full Text PDF PubMed Scopus Google and their ACAT1 and ACAT2 to be the microsomes isolated from the ACAT1 and ACAT2 cells were with cholesterol or sitosterol in compared with The sterol in the microsomes are in I. to the cholesterol of ACAT2 microsomes was 15% lower than that in ACAT1 microsomes. to the cholesterol was to a in both ACAT1 and ACAT2 microsomes. In addition, the sterol was to an when sitosterol-loaded and cyclodextrin was In the sitosterol the sterol the of cholesterol was significantly to from of microsomes with cholesterol or in a The ACAT activity in the microsomes was by incorporation of into ester ACAT1 microsomes, with the activity The microsomes with showed a of ACAT1 activity even though the cholesterol was from to ACAT2 microsomes, with the activity to of the membrane with sitosterol, the ACAT2 activity was by to the that the cholesterol was from to Compared with the ACAT1 microsomes with sterol the ACAT2 microsomes displayed significantly 4-fold with only with and with ACAT2 activity in transfected has been a sitosterol and cholesterol loaded microsomes were with of or The of the sterols of the esterification of both sterols. ACAT1 microsomes, the results were to with the substrate In the microsomes, the rate of ester was than the rate in microsomes loaded with cholesterol the microsomes with sitosterol, the esterification of cholesterol and sitosterol were and that the sterol esterification rate of protein was to that in the the ACAT2 microsomes, the were than was with the ACAT1 microsomes, a difference to was when was used as substrate The rate of esterification was in microsomes compared with the the ACAT2 microsomes were loaded with sitosterol, the esterification rate was with only protein of ester in this the was ester The data showed that when loaded into microsomes, sitosterol was esterified by both ACAT1 and albeit at a compared with cholesterol In addition, the in sitosterol-loaded microsomes displayed sterol substrate the rate of ester by ACAT2 microsomes was than for ACAT1 microsomes the of cholesterol to sitosterol be the for because of the ACAT2 in transfected The of cholesteryl ester to ester formed by ACAT1 and ACAT2 was 1.6 and 7.2, In other the of ACAT1 for cholesterol esterification was greater than for sitosterol In contrast, ACAT2 showed a for esterification of cholesterol compared with sitosterol. The results that ACAT1 and ACAT2 have for sterol of by ACAT1 and ACAT2 in that ACAT1 and ACAT2 in microsomes in their capacity to esterify sitosterol, the sterol specificity of the was in intact cells. To sterol of the containing was with or and of or The was the ACAT1 and ACAT2 cells for and during the 2 of the the cells were with to by incorporation into ester the ACAT of ACAT1 cells to or were ACAT2 cells with the activity ACAT2 cells to or significantly lower and results showed that ACAT2 cells more ACAT activity than ACAT1 cells and that of cells with significantly ACAT2 the the sterol mass of the ACAT1 and ACAT2 cells was ACAT1 cells with or free cholesterol and cholesteryl ester protein and the cells to showed a in free cholesterol and cholesteryl ester mass protein and ACAT2 cells to or free cholesterol and more cholesteryl ester than ACAT1 and although were significantly in ACAT2 cells with protein and were significantly lower and than in ACAT1 of ACAT1 or ACAT2 cells to or cholesterol or sitosterol in in a of cells with the free cholesterol and cholesteryl ester from in cells in The in the free and esterified sitosterol of the ACAT1 and ACAT2 cells were to the free cholesterol and cholesteryl ester mass of cells. ACAT2 cells significantly more free sitosterol and significantly ester than ACAT1 cells. either with sitosterol not to the of cholesterol, rather the sitosterol to be in a In addition to the mass of in the ACAT1 and ACAT2 the of cholesteryl ester and ester formed by the cells were from the with and upon the activity of the in the containing the ACAT1 cells internalized of protein and mg of it to cholesteryl ester the ACAT2 of protein was in the cells with of it in an esterified the of sterol were not the as for the sterol mass data the for of and ester in the ACAT1 and ACAT2 cells was the as for the mass data and with the that the ACAT2 cells ACAT where the cells were to with the ACAT1 cells significantly free sitosterol than the ACAT2 cells In contrast, the ACAT1 cells esterified of the sitosterol compared with only 15% for the ACAT2 cells the in the mass data of Moreover, when the of ester to ACAT activity was the esterification of sitosterol was to for ACAT1 compared with ACAT2. this which is to that in the with microsomes it could be that compared with ACAT1, ACAT2 intact cells more sitosterol from cholesterol and significantly esterified sitosterol of ACAT1 and ACAT2 for ACAT ester in a of by recombinant that either an or of the sterol specificity of LCAT was of the by showed that the cholesterol and sitosterol containing with the ratios and The rate of cholesterol esterification by LCAT was when either the or recombinant were used as substrate LCAT esterified the sitosterol on both the or at of the of esterification of the sterols indicated that LCAT cholesterol 15% more efficiently than sitosterol. The of this was to the with which the cholesterol esterification enzymes, ACAT1, and esterify sitosterol cholesterol. all esterified cholesterol with a greater than their selectivity for the sterols In microsomes loaded with of sitosterol, ACAT2 esterified more cholesterol than sitosterol ACAT1 esterified only more cholesterol than sitosterol. whole cells were with of the internalized sitosterol was esterified by ACAT1 only 15% of it was esterified by ACAT2. In to the sterol esterifying enzymes, the capacity of LCAT to esterify sitosterol on recombinant was of that for cholesterol. results it can be that compared with ACAT1, ACAT2 can more and limit the esterification of sitosterol. On the other the sterol substrate specificity of LCAT to be limited both cholesterol and sitosterol on recombinant to be esterified at The of this were that although both ACAT1 and ACAT2 were able to esterify sitosterol, ACAT2 was at esterifying this plant more many previous studies have the esterification of sitosterol by in sitosterol, several in vivo studies have that the small intestinal which ACAT2 (9Lee R.G. Willingham M.C. Davis M.A. Skinner K.A. Rudel L.L. J. Lipid Res. 2000; 41: 1991-2001Abstract Full Text Full Text PDF PubMed Google could a amount of free sitosterol but that of this plant sterol was esterified and absorbed (11Swell L. Trout Jr., E.C. Field Jr., H. Treadwell C.R. Proc. Soc. Exp. Biol. Med. 1959; : 140-142Crossref PubMed Scopus (5) Google Scholar, 12Bhattacharyya A.K. Lopez L.A. Biochim. Biophys. Acta. 1979; 574: 146-153Crossref PubMed Scopus (32) Google Scholar, 13Bhattacharyya A.K. Am. J. Physiol. 1981; 240: G50-G55PubMed Google Scholar, 14Field F.J. Mathur S.N. J. Lipid Res. 1983; 24: 409-417Abstract Full Text PDF PubMed Google Scholar, 15Ikeda I. Tanaka K. Sugano M. Vahouny G.V. Gallo L.L. J. Lipid Res. 1988; 29: 1583-1591Abstract Full Text PDF PubMed Google Scholar). In addition, microsomes isolated from and which likely both ACAT1 and esterified sitosterol to efficiently than cholesterol (14Field F.J. Mathur S.N. J. Lipid Res. 1983; 24: 409-417Abstract Full Text PDF PubMed Google Scholar, 16Tavani D.M. Nes W.R. Billheimer J.T. J. Lipid Res. 1982; 23: 774-781Abstract Full Text PDF PubMed Google Scholar). with the data from the current the limited esterification of sitosterol in the studies be to either ACAT2 or ACAT1 of sitosterol and cholesterol was in isolated from both ACAT1 and ACAT2 cells. The sitosterol to cholesterol in microsomes from ACAT1 cells was which was than the sitosterol to cholesterol in microsomes from ACAT2 which was This was because of the that was cholesterol in the microsomes from the ACAT2 of sitosterol were in The difference in free cholesterol of ACAT1 and ACAT2 microsomes that the of ACAT activity in the ACAT2 cells are to more of the cholesterol into the esterified form the of free cholesterol in the In contrast, ACAT2 could not the free sitosterol In addition to analysis of microsomes from ACAT1 and ACAT2 studies using intact cells were The data in that ACAT2 cells have a ACAT activity than ACAT1 cells when by incorporation into at the of a with or the data in are into the are that for of the of ACAT2 cells have lower free cholesterol and than ACAT1 a during the because of ACAT2 the the of free sitosterol was and the of ester was lower in the sitosterol-loaded ACAT2 ACAT1 free sitosterol was not efficiently into ester by ACAT2. The small in incorporation into when cholesterol in cyclodextrin was with the ACAT2 cells may reflect the that significantly more has been in ACAT2 and the may have that may have been during the of the with This not when sitosterol in cyclodextrin was with because was greater ACAT activity and cholesterol esterification were in microsomes and whole cells containing ACAT2 compared with ACAT1. However, of sitosterol ACAT2 esterified sitosterol efficiently than ACAT1. it can be that the ACAT enzyme in not esterify sitosterol its incorporation into chylomicrons and its absorption into the However, absorbed sitosterol that is internalized by expressing ACAT1, as and may be esterified it is that cells may not reflect the systems of the whole the the data with the in the that are the difference in sterol specificity displayed by ACAT1 and a from this was that expression of compared with that of ACAT1, to significantly greater of cholesterol The esterification rate of cholesterol by the microsomes compared with the microsomes was greater and In whole the mass of cholesteryl ester was 15% greater and the rate of sterol esterification from incorporation into sterol was in cells expressing ACAT2 compared with ACAT1. The difference in ACAT activity in the and cells may be because of several is that on a basis ACAT2 is more at esterifying cholesterol than ACAT1. However, because both have and is to ACAT1 and the activity of the could not be more likely for the difference in ACAT activity is the more of ACAT1 ACAT2 of ACAT1 and ACAT2 cells with by of the showed that the of ACAT1 and ACAT2 protein were and not This difference in protein likely results in ACAT1 and lower activity in with cells. studies will be to the basis for the difference in ACAT1 and ACAT2 from the results of previous studies (14Field F.J. Mathur S.N. J. Lipid Res. 1983; 24: 409-417Abstract Full Text PDF PubMed Google Scholar, Proc. S. A. PubMed Scopus Google Scholar, Biochim. Biophys. Acta. 1982; PubMed Scopus Google Scholar, E. Mathur S.N. J. Lipid Res. Full Text PDF PubMed Google in ACAT1 and ACAT2 activity were microsomes with cholesterol and This of cholesterol may be not only to an in substrate but also to the ability of cholesterol to as an of ACAT J.C. M.C. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). the current results the that sitosterol may also ACAT2 through an Even though sitosterol in a in cholesterol more cholesteryl ester was in the sitosterol-loaded ACAT2 microsomes This that sitosterol may ACAT2 the cholesterol to be esterified more to ACAT1 and LCAT was to esterify cholesterol compared with sitosterol when the sterols were into recombinant However, the esterification rate of the sterols by LCAT by only results are in with a previous T. 1979; PubMed Scopus Google Scholar) that in the presence of LCAT esterified sitosterol that was into at a rate that was of that for cholesterol. In contrast, another G. J. Clin. Invest. 35: PubMed Google Scholar) that the esterification rate of sitosterol with all lipoprotein in whole plasma was only of that for cholesterol. The of are likely because of the capacity of LCAT to esterify sitosterol on of has been reported that in patients with sitosterolemia, of the sitosterol and of the cholesterol was esterified in In contrast, of the not only the cholesterol but also the sitosterol was esterified in the isolated from (18Salen G. Kwiterovich Jr., P.O. Shefer S. Tint G.S. Horak I. Shore V. Dayal B. Horak E. J. Lipid Res. Full Text PDF PubMed Google Scholar, Eur. J. Clin. Invest. PubMed Scopus Google Scholar). all of the into it to that the ability of LCAT to sitosterol from cholesterol is limited and should not be with the more limited activity of LCAT on In the current has that ACAT1, and LCAT can all esterify sitosterol. However, ACAT2 displayed the capacity to cholesterol from sitosterol and limit sitosterol The sterol specificity of ACAT2 may reflect an in vivo role in the absorption of sitosterol and other plant and shellfish sterols. studies are to the of
No takes yet. Share an insight, caveat, or question.
Temel et al. (2003) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: