References: Lecithin
Biochemistry. 1989 Jun 27;28(13):5354-66.
Coenzyme binding by 3-hydroxybutyrate dehydrogenase, a lipid-requiring enzyme: lecithin acts as an allosteric modulator to enhance the affinity for coenzyme.
Rudy B, Dubois H, Mink R, Trommer WE, McIntyre JO, Fleischer S.
Department of Chemistry, University of Kaiserslautern, FRG.
The role of phospholipid in the binding of coenzyme, NAD(H), to 3-hydroxybutyrate dehydrogenase, a lipid-requiring membrane enzyme, has been studied with the ultrafiltration binding method, which we optimized to quantitate weak ligand binding (KD in the range 10-100 microM). 3-Hydroxybutyrate dehydrogenase has a specific requirement of phosphatidylcholine (PC) for optimal function and is a tetramer quantitated both for the apodehydrogenase, which is devoid of phospholipid, and for the enzyme reconstituted into phospholipid vesicles in either the presence or absence of PC. We find that (i) the stoichiometry for NADH and NAD binding is 0.5 mol/mol of enzyme monomer (2 mol/mol of tetramer); (ii) the dissociation constant for NADH binding is essentially the same for the enzyme reconstituted into the mixture of mitochondrial phospholipids (MPL) (KD = 15 +/- 3 microM) or into dioleoyl-PC (KD = 12 +/- 3 microM); (iii) the binding of NAD+ to the enzyme-MPL complex is more than an order of magnitude weaker than NADH binding (KD approximately 200 microM versus 15 microM) but can be enhanced by formation of a ternary complex with either 2-methylmalonate (apparent KD = 1.1 +/- 0.2 microM) or sulfite to form the NAD-SO3- adduct (KD = 0.5 +/- 0.1 microM); (iv) the binding stoichiometry for NADH is the same (0.5 mol/mol) for binary (NADH alone) and ternary complexes (NADH plus monomethyl malonate); (v) binding of NAD+ and NADH together totals 0.5 mol of NAD(H)/mol of enzyme monomer, i.e., two nucleotide binding sites per enzyme tetramer; and (vi) the binding of nucleotide to the enzyme reconstituted with phospholipid devoid of PC is weak, being detected only for the NAD+ plus 2-methylmalon
Kidney Int. 1993 Jul;44(1):91-7.
Role of elevated lecithin: cholesterol acyltransferase and cholesteryl ester transfer protein activities in abnormal lipoproteins from proteinuric patients.
Dullaart RP, Gansevoort RT, Dikkeschei BD, de Zeeuw D, de Jong PE, Van Tol A.
Department of Endocrinology, State University Hospital Groningen, The Netherlands.
Lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP) are key factors in the esterification of free cholesterol, and the distribution of cholesteryl ester among lipoproteins in plasma. Alterations in these processes may play a role in the lipoprotein abnormalities associated with glomerular proteinuria. The activities of LCAT and CETP were measured using excess exogenous substrate assays in nine patients with nephrotic-range proteinuria and in 18 matched controls. The proteinuria-lowering effect of four weeks of angiotensin converting enzyme (ACE) inhibition with enalapril was also studied. Plasma very low lipoprotein and low density lipoprotein (VLDL and LDL) cholesterol, triacylglycerol and apolipoprotein B levels were significantly elevated in the patients compared with controls. High density lipoprotein (HDL) total cholesterol, free cholesterol, cholesteryl ester and the free cholesterol/cholesteryl ester ratio in HDL were lower. Total plasma apolipoprotein A1 was normal. Plasma LCAT and CETP activities were elevated in the patients by 30% (P < 0.01) and by 39% (P < 0.01), respectively, and were both inversely related to serum albumin. VLDL and LDL cholesterol levels were positively related to LCAT and CETP activities, whereas the HDL free cholesterol content was inversely related to LCAT activity. ACE inhibition resulted in a 40% reduction of proteinuria, a partial normalization of LCAT activity, and a decrease in VLDL and LDL cholesterol. In conclusion, elevated activities of LCAT and CETP may provide a mechanism that contributes to the low proportion of cholesterol in HDL relative to that in
J Pediatr Surg. 1994 Aug;29(8):1020-3; discussion 1023-4.
Amniotic fluid phospholipid analysis in the fetus with congenital diaphragmatic hernia.
Sullivan KM, Hawgood S, Flake AW, Harrison MR, Adzick NS.
Fetal Treatment Center, University of California, San Francisco 94143-0570.
The substantial morbidity and mortality of congenital diaphragmatic hernia (CDH) is attributed to the pulmonary hypoplasia caused by the presence of abdominal viscera in the chest during intrauterine life. Recent experimental studies suggest that surfactant deficiency may also contribute to CDH pathophysiology. Clinically, the amniocentesis-derived lecithin to sphingomyelin (L/S) ratio and phosphatidylglycerol (PG) data are used to assess fetal lung maturity. We have performed amniotic fluid phospholipid analyses at 33 to 38 weeks' gestation in 18 fetuses with prenatally diagnosed CDH to assess fetal lung maturity, plan optimal timing for delivery, and selectively employ prenatal glucocorticoid or postnatal surfactant therapy. Compared with published control values from uncomplicated pregnancies, there was no difference in the L/S ratio or PG in the CDH fetus. Based on amniotic fluid phospholipid data, the human CDH fetus is not surfactant-deficient.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7965499&dopt=Abstract lecithin
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