References: Lecithin
Arterioscler Thromb. 1994 Jul;14(7):1137-45.
Characterization of subspecies of apolipoprotein A-I-containing lipoprotein in homozygotes for familial lecithin:cholesterol acyltransferase deficiency.
Ohta T, Hattori S, Nakamura R, Horiuchi S, Frohlich J, Takata K, Ikeda Y, Saito Y, Matsuda I.
Department of Pediatrics, Kumamoto University School of Medicine, Japan.
We characterized the two species of lipoproteins containing apolipoprotein A-I (apoA-I), one containing only apoA-I (LpA-I) and the other containing apoA-I and apoA-II (LpA-I/A-II), in four homozygotes for familial lecithin: cholesterol acyltransferase (LCAT) deficiency. Two homozygotes lacked both LCAT mass and activity, whereas the other two had some residual LCAT mass and activity. In these patients, the amount of all apoA-I-containing lipoproteins was one fourth that of normal control subjects, and > 60% was LpA-I. The chemical composition of both LpA-I and LpA-I/A-II is characterized by markedly decreased ratios of neutral to polar lipids compared with those of normals and the sizes of LpA-I and LpA-I/A-II particles are shifted to smaller and larger diameter ranges when compared with those of normal particles. Changes in particle diameter are also reflected in slower electrophoretic mobilities of both LpA-I and LpA-I/A-II particles. All of these abnormalities were more evident in the two homozygotes who lacked LCAT activity. Incubation of LCAT-deficient plasma with LCAT markedly corrected the chemical and physical abnormalities in both LpA-I and LpA-I/A-II particles. These data, taken together, emphasize the importance of LCAT in modifying the chemical composition, size, and shape of LpA-I and LpA-I/A-II particles.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8018670&dopt=Abstract lecithin
Biochim Biophys Acta. 1993 Mar 14;1146(2):178-82.
Archaebacterial lipids: highly proton-impermeable membranes from 1,2-diphytanyl-sn-glycero-3-phosphocholine.
Yamauchi K, Doi K, Yoshida Y, Kinoshita M.
Department of Bioapplied Chemistry, Faculty of Engineering, Osaka City University, Japan.
Unlike ordinary glycero-lipids such as egg-yolk lecithin, 1,2-diphytanyl-sn-glycero-3-phosphocholine, which was employed as a model lipid of archaebacterial acidophiles, gave liposomal membranes which were highly resistant to proton permeation in a wide temperature range (about 10-50 degrees C); the permeability coefficient and activation energy of the flux were 0.7 x 10(-5) cm/s at 20 degrees C and 24.5 kcal/mol, respectively. The high resistance to proton flow was attributed to a fluid and bulky isoprenoid chain-layer of the membrane.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8383997&dopt=Abstract lecithin
Science. 1989 Apr 7;244(4900):82-5. ["Protein","window.top.location='Laxative online source: www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?db=PubMed&cmd=Display&dopt=pubmed_protein&from_uid=2704992'","",""],["Structure","window.top.location='Laxative online source: www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?db=PubMed&cmd=Display&dopt=pubmed_structure&from_uid=2704992'","",""],["3D Domains","window.top.location='Laxative online source: www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?db=PubMed&cmd=Display&dopt=pubmed_domains&from_uid=2704992'","",""],
Enhanced activity and altered specificity of phospholipase A2 by deletion of a surface loop.
Kuipers OP, Thunnissen MM, de Geus P, Dijkstra BW, Drenth J, Verheij HM, de Haas GH.
Department of Biochemistry, University of Utrecht, The Netherlands.
Protein engineering and x-ray crystallography have been used to study the role of a surface loop that is present in pancreatic phospholipases but is absent in snake venom phospholipases. Removal of residues 62 to 66 from porcine pancreatic phospholipase A2 does not change the binding constant for micelles significantly, but it improves catalytic activity up to 16 times on micellar (zwitterionic) lecithin substrates. In contrast, the decrease in activity on negatively charged substrates is greater than fourfold. A crystallographic study of the mutant enzyme shows that the region of the deletion has a well-defined structure that differs from the structure of the wild-type enzyme. No structural changes in the active site of the enzyme were detected.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2704992&dopt=Abstract lecithin
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