| 11. |
- Ncube, Ignatious, et al.
(författare)
-
Fatty acid selectivity of a lipase purified from Vernonia galamensis seed
- 1995
-
Ingår i: Biochimica et Biophysica Acta - Lipids and Lipid Metabolism. - 0005-2760. ; 1257:2, s. 149-156
-
Tidskriftsartikel (refereegranskat)abstract
- Vernonia galamensis is an annual herb whose seed oil contains high levels of an epoxy fatty acid, vernolic (cis-12,13-epoxy cis-9-octadecenoic) acid. The seed also contains lipase activity in the dormant state. A lipase was purified from the seed and its substrate specificity studied in isooctane. The lipase shows pronounced selectivity for the native triacylglycerol, trivernolin. The rate of hydrolysis of triolein, the corresponding non epoxy triacylglycerol, is only 3% of that of trivernolin. In the acidolysis of tricaprylin using a mixture of fatty acids, the Vernonia lipase also showed selectivity for vernolic acid. Michaelis-Menten kinetics of the hydrolysis of triacylglycerols revealed that the observed high selectivity of the Vernonia lipase for trivernolin was mainly due to a higher Vmax for trivernolin. The Vmax value for the hydrolysis of trivernolin was 5 times higher than that for triolein. This novel substrate specificity is an adaptation by the seed lipase to the triacylglycerols of the seed oil that contain up to 80% vernolic acid.
|
|
| 12. |
|
|
| 13. |
- Nilsson-Ehle, Peter, et al.
(författare)
-
Intra- and extracellular forms of lipoprotein lipase in adipose tissue
- 1976
-
Ingår i: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002. ; 431:1, s. 147-156
-
Tidskriftsartikel (refereegranskat)abstract
- The location of lipoprotein lipase activity in rat adipose tissue was studied using intact epididymal fat pads, isolated adipocytes, and lipoprotein lipase activity secreted from adipocytes as enzyme sources. The enzyme activities of these preparations were characterized by gel filtration. The method used for isolation of adipocytes had been modified to minimize activation of lipoprotein lipase during the procedures. Extracts of intact adipose tissue separated into two major lipoprotein lipase activity peaks, designated "a" and "b", the "a" fraction representing about 30 (fasted rats) to 50% (fed rats) of the total enzyme activity. An intermediate fraction (designated "i") was frequently observed. Extracts of isolated adipocytes from fed rats contained about 35% and those from fasted rats about 65% of the lipoprotein lipase activity present in intact tissue. The "b" fraction constituted 80--97% of the adipocyte lipoprotein lipase activity. In contrast, the enzyme activity secreted from the adipocytes contained only the "a" and "i" fractions. These data implicate the existance of one intracellular form of lipoprotein lipase (corresponding to the "b" fraction), different from extracellular forms of the enzyme (corresponding to fractions "a" and "i"). A transformation of the intracellular to the extracellular forms appears to occur in conjunction with secretion of enzyme from the fat cell.
|
|
| 14. |
|
|
| 15. |
|
|
| 16. |
|
|
| 17. |
|
|
| 18. |
- Sundler, R, et al.
(författare)
-
Sources of diacylglycerols for phospholipid synthesis in rat liver
- 1974
-
Ingår i: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002. ; 337:2, s. 54-248
-
Tidskriftsartikel (refereegranskat)abstract
- The biosynthesis of molecular species of phosphatidylethanolamine and phosphatidylcholine in isolated rat liver parenchymal cells was studied with [32P]phosphate and [3H]glycerol as precursors. Addition to the cells of albumin-bound oleic or linoleic acid resulted in the synthesis of high proportions of dioleoyl- or dilinoleoyl-phospholipids, especially from labeled glycerol. The fact that these species contained a lower proportion of 32P than of 3H indicated that other diacylglycerols than those newly synthesized via phosphatidic acids took part in phospholipid synthesis. The composition of such diacylglycerols could be calculated and was found (a) to be essentially unaffected by the presence of oleic or linoleic acid during incubation, and (b) to be very similar to the mass composition of diacylglycerol units in the phosphatidyl-cholines. This suggests that they had been formed from the phosphatidylcholines, probably by the reversal of the cholinephosphotransferase (EC 2.7.8.2) reaction. These diacylglycerols contributed about 26 and 13 % of the total diacylglycerols incorporated into phosphatidylethanolamines and phosphatidylcholines, respectively.
|
|
| 19. |
|
|
| 20. |
|
|
