Overt and latent activities of diacylglycerol acyltransferase in rat liver microsomes: Possible roles in very-low-density lipoprotein triacylglycerol secretion

被引:103
作者
Owen, MR [1 ]
Corstorphine, CC [1 ]
Zammit, VA [1 ]
机构
[1] HANNAH RES INST,AYR KA6 5HL,SCOTLAND
关键词
D O I
10.1042/bj3230017
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The possibility that triacylglycerol (TAG) synthesis occurs on both aspects of the endoplasmic-reticular membrane during the process of incorporation of TAG into secreted very-low-density lipoprotein (VLDL) [Zammit (1996) Biochem. J. 314, 1-14] was investigated by measuring the latency of diacylglycerol acyltransferase (DGAT) in microsomal fractions obtained from rat liver homogenates. Permeabilization of microsomes with taurocholate resulted in the doubling of the activity, indicating that DGAT activities of approximately equal magnitude occur on either aspect of the microsomal membrane. The taurocholate concentrations required for exposure of the latent activity of DGAT were identical with those that resulted in the exposure of marker enzymes for the lumen of the endoplasmic reticulum. Fractionation of the microsomes into smooth and rough populations indicated that the distribution of overt and latent DGAT activities was the same throughout. The possibility that taurocholate effects may result from non-specific activation of the overt enzyme was excluded by employing the channel-forming peptide alamethicin to effect permeabilization, and by varying the mode of delivery of diacylglycerol substrate to the microsomal membranes. Permeabilization using alamethicin gave a slightly higher latent/overt ratio for DGAT. The possible roles of overt and latent DGAT activities in the synthesis and secretion of TAG by the liver are discussed.
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页码:17 / 21
页数:5
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共 36 条
[11]   INTRACELLULAR EVENTS IN THE ASSEMBLY OF VERY-LOW-DENSITY-LIPOPROTEIN LIPIDS WITH APOLIPOPROTEIN-B IN ISOLATED RABBIT HEPATOCYTES [J].
CARTWRIGHT, IJ ;
HIGGINS, JA .
BIOCHEMICAL JOURNAL, 1995, 310 :897-907
[12]   EVIDENCE THAT BIOSYNTHESIS OF PHOSPHATIDYLETHANOLAMINE, PHOSPHATIDYLCHOLINE, AND TRIACYLGLYCEROL OCCURS ON CYTOPLASMIC SIDE OF MICROSOMAL VESICLES [J].
COLEMAN, R ;
BELL, RM .
JOURNAL OF CELL BIOLOGY, 1978, 76 (01) :245-253
[13]  
COLEMAN RA, 1983, ENZYMES, V16, P605
[14]  
FUKUDA N, 1982, J BIOL CHEM, V257, P4066
[15]  
GIBBONS GF, 1994, J LIPID RES, V35, P1801
[16]   INTRACELLULAR TRIACYLGLYCEROL LIPASE - ITS ROLE IN THE ASSEMBLY OF HEPATIC VERY-LOW-DENSITY LIPOPROTEIN (VLDL) [J].
GIBBONS, GF ;
WIGGINS, D .
ADVANCES IN ENZYME REGULATION, VOL 35, 1995, 35 :179-198
[17]  
GLAUMAN H, 1976, J CELL BIOL, V64, P356
[18]   Inhibition of the microsomal triglyceride transfer protein blocks the first step of apolipoprotein B lipoprotein assembly but not the addition of bulk core lipids in the second step [J].
Gordon, DA ;
Jamil, H ;
Gregg, RE ;
Olofsson, SO ;
Boren, J .
JOURNAL OF BIOLOGICAL CHEMISTRY, 1996, 271 (51) :33047-33053
[19]  
HANDE W, 1972, ACTA BIOL MED GER, V28, P963
[20]  
HIGGINS JA, 1987, J LIPID RES, V28, P268