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PubMed1981

Induction and specificity of a (cytochrome P-450)-dependent laurate in-chain-hydroxylase from higher plant microsomes.

The substrate and product specifities of the (cytochrome P-450)-dependent laurate monooxygenase from tuber tissues of Jerusalem artichoke (Helianthus tuberosus L.) were investigated. The plant enzyme appeared strictly specific for the C12 free fatty acid and produced a mixture of C-8, C-9 and C-10 hydroxylated lauric acids, the C-9 derivative being predominant. No C-12 or C-11 hydroxylated laurates were detected. The activity of the enzyme, which was not detectable in the intact tuber, was induced by slicing and aging the tissues on water, and strongly superinduced by the addition of manganese and phenobarbital to the aging medium. Regulation of laurate hydroxylase was clearly independent from that of cinnamic acid 4-hydroxylase, another plant cytochrome P-450 enzyme.

Cytochrome P-450 Enzyme System↗
PubMedDate not supplied

Incorporation of label from acetate and laurate into the mannan of Leishmania donovani via the glyoxylate cycle.

Leishmania donovani promastigotes in late-stationary phase incorporated label from [2-14C]acetate and [1-14C]laurate into the mannose residues of mannan, thus confirming the presence of a functional glyoxylate bypass in these parasitic protozoa. Isolated, washed calls also incorporated label from [2-14C]acetate and [1-14C]laurate into mannan during a 1-hr incubation in buffer. Glucose had no effect on label incorporation into mannan, but glutamate caused over a four-fold increase in incorporation from [2-14C]acetate and a 2.4-fold increase from [1-14C]laurate. Staurosporine, a protein kinase inhibitor that inhibits glutamate and alanine oxidation, did not inhibit label incorporation from [2-14C]acetate into mannan. Hyperosmolality caused about a 33% inhibition of label incorporation into mannan. These results show the glyoxylate cycle and/or the subsequent biosynthetic pathway from fructose-6-phosphate to mannan are subject to regulation.

Acetates↗
PubMed1994

Reduction in acid tolerance of Streptococcus downeii by fluoride and potassium laurate.

Streptococcus downeii MFe28 maintains a transmembrane pH gradient at low extracellular pH values using energy from glucose metabolism. The metabolic activity was measured in saturating glucose solutions using a pH-stat, and results were expressed as rates of titratable acid production at defined pH values. The tolerance to acid shock was studied in terms of the ability of cells to resume acid production at pH 8.0 following short-term exposure to low-pH environments. The results with control cells showed an optimum rate of acid production at pH 8.0. The activity extended to pH 4.5 with a half-maximal rate at pH 5.4. Addition of carbonyl cyanide-m-chlorophenylhydrazone, potassium laurate, or potassium fluoride inhibited acid production at lower but not at higher pH values. Inhibition by carbonyl cyanide-m-chlorophenylhydrazone and fluoride was found to be fully reversible at pH 8.0 when compared to control cells. In contrast, laurate inhibited irreversibly at pH values of 6.0 and below. The acid tolerance of S. downeii was severely compromised by laurate, and this action could be useful in dental caries control.

Acids↗
PubMed1996

Micellization and solubilization behavior of sucrose laurate, a new pharmaceutical excipient.

The micellization and solubilization properties of sucrose laurate have been investigated. Solubilization experiments showed that numerous poorly water-soluble drug substances could be solubilized by aqueous sucrose laurate solutions; the solubilization was uncomplicated and the maximum solubilizate concentration was high. Laser light scattering investigations proved that solutions containing pure sucrose monolaurate formed spheroidally shaped micelles with a hydrodynamic radius of 29.2 A, which behaved like ideal particles, showing no solute-solute interactions. Surprisingly, the hydrodynamic radii of the sucrose monolaurate micelles were hardly changed by the introduction of 0.20% cyclosporin-A. The addition of sucrose dilaurate, the main impurity of the sucrose laurate product, however, resulted in large and polydisperse structures. Considering the critical packing parameters, the light scattering results could be explained by assuming a transformation of the spherical micelle into a disk with rounded edge.

Diffusion↗
PubMed1990

Biosynthesis of lipid A in Escherichia coli. Acyl carrier protein-dependent incorporation of laurate and myristate.

In previous studies we described enzyme(s) from Escherichia coli that transfer two 3-deoxy-D-manno-octulosonate (KDO) residues from two CMP-KDO molecules to a tetraacyldisaccharide-1,4'-bis-phosphate precursor of lipid A, termed lipid IVA (Brozek, K. A., Hosaka, K., Robertson, A. D., and Raetz, C. R. H. (1989) J. Biol. Chem. 264, 6956-6966). The product, designated (KDO)2-IVA, can be prepared in milligram quantities and/or radiolabeled with 32P at position 4' of the IVA moiety. We now demonstrate the presence of enzymes in E. coli extracts that transfer laurate and/or myristate residues from lauroyl or myristoyl-acyl carrier protein (ACP) to (KDO)2-IVA. Thioesters of coenzyme A are not substrates. The cytosolic fraction catalyzes rapid acylation with lauroyl-ACP, but not with myristoyl, R-3-hydroxymyristoyl, palmitoyl, or palmitoleoyl-ACP. The membrane fraction transfers both laurate and myristate to (KDO)2-IVA. Evidence for the enzymatic acylation of (KDO)2-IVA is provided by (a) conversion of [4'-32P](KDO)2-IVA to more rapidly migrating products in the presence of the appropriate acyl-ACP, (b) incorporation of [1-14C]laurate or [1-14C]myristate into these metabolites in the presence of (KDO)2-IVA, (c) fast atom bombardment-mass spectrometry, and (d) 1H NMR spectroscopy. At protein concentrations less than 0.5 mg/ml, the acylation of (KDO)2-IVA by the cytoplasmic fraction is absolutely dependent upon the addition of exogenous acyl-ACP. These acyltransferases cannot utilize lipid IVA as a substrate, demonstrating that they possess novel KDO recognition domains. The unusual substrate specificity of these enzymes provides compelling evidence for their involvement in lipid A biosynthesis. Depending on the conditions it is possible to acylate (KDO)2-IVA with 1 or 2 lauroyl residues, with 1 or 2 myristoyl residues, or with 1 of each.

Acyl Carrier Protein↗
PubMed1994

Structural determination and packing analysis of a cholesteryl caprate/cholesteryl laurate solid solution.

This paper describes the X-ray crystal structure analysis of a cholesteryl ester solid solution, cholesteryl decanoate/cholesteryl laurate, grown from a bulk concentration with molar ratio 0.56/0.43. The unit cell is monoclinic with a = 12.969, b = 9.048, c = 31.137 A, and beta = 91.12 degrees and the space group P2(1) with Z = 4 (two molecules per asymmetric unit). The cell constants closely represent an average value of crystal parameters for the two pure components (hence, nearly corresponding to Vegard's law). Although the overall monolayer 1 lamellar packing is superficially similar to the earlier-studied cholesteryl undecanoate/cholesteryl laurate solid solution, a more partitioned distribution of acyl chains, i.e., a microfractionation corresponding to the observed nonideal phase behavior, is suggested. The behavior is similar to that found for n-paraffin binaries cooled below a binodal phase boundary. Although it cannot be detected conclusively in this determination (due to high thermal motion of terminal acyl chain atoms), the non-stoichiometric combination of components also requires some partial occupancy of atomic sites on the chain termini. This structural arrangement is contrasted with the alternative expression found earlier for the more ideal undecanoate/laurate solid solution, i.e., random co-packing leading to fractional atomic occupancy in an average laurate structure. The final weighted R factor for 4578 reflections is 0.138.

Cholesterol Esters↗
PubMed2006

Studies of reaction parameters on synthesis of Citronellyl laurate ester via immobilized Candida rugosa lipase in organic media.

Immobilized Candida rugosa lipase was used for the synthesis of citronellyl laurate from citronellol and lauric acid. Screening of different types of support (Amberlite MB-1 and Celite) for immobilization of lipase and solvent (n-hexane, n-heptane, and iso-octane) and optimization of reaction conditions, such as catalyst loading, effect of substrates molar ratio and temperature, have been studied. The maximum enzyme activity was obtained at 310 K. The immobilized C. rugosa lipase onto Amberlite MB-1 support was found to be the best support with a conversion of 89% of citronellyl laurate ester in iso-octane compared to Celite 545. Deactivation of C. rugosa lipase at 313, 318 and 323 K were observed. Ordered bi bi mechanism with dead end complex of lauric acid was found to fit the initial rate data and the kinetic parameters were obtained by non-linear regression analysis.

Acyclic Monoterpenes↗
PubMed1997

Gas-liquid chromatographic properties of positional isomers of methyl thia, selena, and tellura laurate analogs.

Gas-liquid chromatographic analyses of three complete series of synthetic positional isomers of methyl thia, selena, and tellura laurate analogs were carried on a nonpolar (SE-30) and a polar (SP-2330) stationary phase. The average ECL (equivalent chain length) values of the thia, selena, and tellura laurate on SE-30 stationary phase were 13.8, 14.8, and 15.7, respectively, while on SP-2330 the average values for the same series were 17.1, 19.0, and 19.1, respectively. Positional isomers with the heteroatom at the 2-position exhibited the lowest ECL values, while those with the heteroatom at the omega-1 position gave the highest ECL values and were readily separated from the other positional isomers of the same series of analogs by this technique.

Chromatography, Gas↗
PubMed2002

Tricarbocyanine cholesteryl laurates labeled LDL: new near infrared fluorescent probes (NIRFs) for monitoring tumors and gene therapy of familial hypercholesterolemia.

For monitoring low-density lipoprotein receptors (LDLr) in tumors and in livers of patients with familial hypercholesterolemia (FH) treated with gene therapy, a series of tricarbocyanine cholesteryl laurates were synthesized with the cholesteryl laurate moiety serving as the lipid-chelating anchor for low-density lipoprotein (LDL). One of these conjugates, TCL17, was successfully used to label LDL to give a new NIRF, TCL17-LDL. Ex vivo biological studies on an LDLr overexpressing tumor model, human hepatoblastoma G(2) (HepG(2)), confirmed that this NIRF were internalized selectively by the tumor and detected with high sensitivity by a low-temperature 3-D redox scanner.

Animals↗
PubMed2001

Enzymatic modification of high-laurate canola to produce margarine fat.

Stearic acid was enzymatically transesterified with high-laurate canola using a nonspecific lipase from Candida antarctica to produce structured lipids (SL) suitable for margarine application. Stearic acid levels ranged from 10 to 40 wt % of high-laurate canola oil. Differential scanning calorimetry was used to evaluate melting characteristics of the transesterified products. A stearic acid level of 30% was found to best match the melting characteristics of fat extracted from commercially available stick margarine. This SL was used to prepare nonrefrigerated and refrigerated margarine samples. Refrigerated margarine was prepared using 60% SL and 40% canola oil, whereas 100% SL was used for the nonrefrigerated margarine. Slip melting point, solid fat content, and hardness index were determined for all samples. Application of a dynamic temperature step using a dynamic stress rheometer showed complete breakdown of the commercial stick margarine and the experimental refrigerated margarine at approximately 30 degrees C and complete breakdown of the nonrefrigerated margarine at approximately 35 degrees C. Addition of canola oil to the SL improved spreadability at refrigeration temperatures and reduced the hardening effect of lauric acid in the SL. The nonrefrigerated margarine was spreadable at room temperature and exhibited no oil exudation or phase separation.

Calorimetry, Differential Scanning↗
PubMed1992

Effects of diethyl phthalate and other plasticizers on laurate hydroxylation in rat liver microsomes.

Diethyl phthalate (DEP) is used in pharmaceutical coatings, cosmetics, and plastic films to wrap foods. There is a health concern associated with the exposure to certain phthalate esters because they belong to a class of compounds referred to as peroxisome proliferators which have been shown to increase the incidence of liver tumors when administered to rats. In this study, we have compared DEP to four other commonly used plasticizers, 2-diethylhexyl phthalate (DEHP), dibutyl phthalate (DBP), 2-diethylhezyl adipate (DEHA), and acetyltributyl citrate (ATBC), for their ability to induce the cytochrome P450-mediated fatty acid omega-hydroxylation system, which is one of the initial cellular responses when animals are treated with peroxisome proliferators. The administration of DEHP, DBP, and DEHA to rats increased the specific activity of laurate 12-hydroxylase from 2.8 +/- 1.1 in control rats to 30.3 +/- 11.6, 14.5 +/- 4.1, and 9.7 +/- 1.9 nmol 12-hydroxylaurate formed/min/nmol P450, respectively. In contrast, laurate 12-hydroxylase activity in DEP- and ATBC-treated rats were 4.4 +/- 1.2 and 4.4 +/- 1.0 nmol 12-hydroxylaurate formed/min/nmol P450, respectively. In addition, whereas DEHP increased peroxisomal palmitoyl-CoA oxidation 6-fold, DEP increased this activity only 1.3-fold. Two protein bands, at 51 and 52 kDa, were found to increase 6- to 12-fold in microsomes of DEHP-, DBP-, and DEHA-treated rats, but these bands were increased only 2-fold in DEP- or ATBC-treated rats.

Animals↗
PubMed1988

Cobinding of bilirubin and laurate to human serum albumin: spectroscopic characterization of stoichiometric complexes.

Light absorption and CD spectra of bound bilirubin and albumin fluorescence spectra have been recorded from mixtures containing albumin, A, bilirubin, B, and laurate, L, in Tris-NaCl buffer at pH 8.2, 25 degrees C. Concentrations of the corresponding stoichiometric complexes, ABiLj, for i = 0/3 and j = 0/3, have been calculated from previously determined stoichiometric cobinding constants (H. Sato et al. (1988) Arch. Biochem. Biophys. 260, 811-821). Spectral data of the complexes have finally been found by iterative computer fitting using the principle of several acceptable solutions (R. Brodersen et al. (1987) Eur. J. Biochem. 169, 487-495). The results were utilized at the microscopic level to investigate ligand-induced conformational changes. When laurate was bound to AB, a decrease of the distance between Trp-214 and the bound bilirubin occurred, as measured according to Förster's principle. The distances were 21.9 +/- 0.3 A in AB, 19.7 +/- 0.3 A in ABL, and 17.9 +/- 0.2 A in ABL2.

Bilirubin↗
PubMed1989

Point mutations at threonine-301 modify substrate specificity of rabbit liver microsomal cytochromes P-450 (laurate (omega-1)-hydroxylase and testosterone 16 alpha-hydroxylase).

Thr-301 of cytochrome P-450 (laurate (omega-1)-hydroxylase) was replaced by Ser, Val, Ile, or Asn via site-directed mutagenesis. The Ser-, Val-, and Asn-mutants had lower laurate (omega-1)-hydroxylase activities than the wild-type P-450. The mutation to Ser did not affect caprate (omega-1)-hydroxylase activity and rather increased caprate omega-hydroxylase activity, but the Val- and Asn-mutants could not hydroxylate caprate. The Ile-mutant was devoid of the hydroxylase activities. The mutation also led to changes in the affinities for the fatty acids and exogenous ligands. Replacement of Thr-301 of cytochrome P-450 (testosterone 16 alpha-hydroxylase) by Ser or Val also affected the activities toward testosterone and progesterone in different ways. These findings indicate that residue 301 of the P-450s plays an important role in determining their substrate specificities.

Amino Acid Sequence↗
PubMed1993

Role of thyroid state on induction by ciprofibrate of laurate hydroxylase and peroxisomal enzymes in rat liver microsomes.

The effects of hypothyroidism and hyperthyroidism upon liver microsomal omega-laurate hydroxylase activity (cytochrome P450 IV A1-dependent), peroxisome proliferation marker enzyme activities and acyl CoA oxidase (AOX) expression induced by ciprofibrate (2 mg/kg/day during 8 days) were studied in the male Wistar rat so as to clarify firstly the possible involvement of thyroid hormones in the modification of peroxisomal ciprofibrate-induced enzyme activities in relation to hepatic microsomal cytochrome P450 IV A1 induction, and secondly the possible direct effect of thyroid hormones on the gene expression of specific peroxisomal enzymes. No significant change was found in the ciprofibrate-induced omega-laurate hydroxylase activity in hypothyroid rats or in rats that had received a large dose of triiodothyronine (LT3), suggesting that the thyroid hormone does not interfere with the peroxisome proliferation process through such an indirect mechanism. The induction by ciprofibrate [2-(4-(2-2dichlorocyclopropyl)phenoxyl-2methyl-propion ic acid)] of mitochondrial alpha-glycerolphosphate dehydrogenase and microsomal bilirubin UDPGT was decreased about 3-fold and 1.5-fold, respectively, while the induction of peroxisomal AOX, carnitine acetyl transferase and enoyl CoA hydratase enzyme activities was decreased by 36%, 34% and 22% in thyroidectomized animals, as compared to euthyroid animals. However, no significant changes in the quantity of peroxisomal proteins and in the AOX mRNA level were noted. The administration of large doses of LT3 to normal rats decreased the peroxisomal ciprofibrate AOX enzyme induction with a marked concomitant decrease in the AOX mRNA level. This suggests that high doses of LT3 enhance the turnover of some specific mRNAs or down regulate the peroxisome proliferator receptor. Our results also do not exclude inhibition of catabolic activity towards AOX which depends on thyroid hormone.

Animals↗
PubMed2000

Permeation liquid membrane metal transport: studies of complex stoichiometries and reactions in Cu(II) extraction with the mixture 22DD-laurate in toluene/phenylhexane

The role of lauric acid (LAH) in the transport of copper(II) through a permeation liquid membrane (PLM) comprising 1,10-didecyldiaza-18-crown-6 (22DD) and lauric acid (ratio 1:1) in 1:1 v/v toluene/phenylhexane has been investigated by determining the stoichiometry of metal extraction and of the metal complex formed in the organic phase by performing 1H NMR and liquid/liquid and liquid/membrane extraction measurements. In the absence of copper(II), the 1H NMR data suggest that there is a strong interaction between the proton of LAH and the nitrogen of the 22DD macrocycle but no interaction between the aliphatic long chains of LAH and 22DD. Thus, in the organic solution, the two compounds are associated as (22DD-H)(+)-LA-, the laurate being away from (22DD-H)+. The signal intensity of the acidic proton was found to decrease when the metal Pb(II) was incorporated by the carrier after its extraction from the aqueous phase. Additionally, liquid/liquid as well as liquid/membrane extraction results reveal that Cu(II) extraction proceeds via the loss of two protons from the organic phase. The Cu(II) is found to be located in the 22DD cavity and the stoichiometry of the complex in the organic phase is (22DD-Cu)(2+)-2LA-. Metal extraction is governed by 22DD and laurate acts only as counteranion. An unexpected feature was observed in the liquid/liquid extraction which was that, at low 22DD and LAH concentrations, the slope for log(Kp) = f(pH) was 2 whereas it was much lower at high carrier concentration. This unexpected result seems to stem from impurities present in 22DD: only 0.1 mol% of impurity can indeed influence the exchange ratio of Cu(II) and H+. This type of anomaly, however, is not found in the normal procedure of liquid/membrane extraction possibly due to the lower carrier/metal molar ratio which is used in the classical PLM conditions.

Journal Article↗
PubMed1998

Residues and metabolism of 19-nortestosterone laurate in steers.

The illegal use of 19-nortestosterone (19NT; 4-estren-17 beta-ol-3-one; nandrolone) and its esters in livestock, for growth promotion purposes, has been widely reported in the European Union. The target residues for surveillance of abuse in bovine urine and bile samples are 17 alpha- and 17 beta-19NT, although this choice of target residues is not based on in vivo radiotracer biotransformation data. In this study, four steers were administered [3H2]- and [2H3] 17 beta-19NT laurate (2 mg kg-1 body mass) by intramuscular injection and blood, urine, faeces and bile samples were taken for 30 d until slaughter, after which tissues were sampled for total residue analysis. Total plasma radiolabelled residues reached a maximum of 56.3 +/- 15.9 pmol ml-1 at 36 h and were still appreciable (13.3 +/- 1.6 pmol ml-1) 30 d after treatment. Throughout the study period, total residue concentrations in bile (about 2-16 nmol ml-1), urine and faeces (0.5-3 nmol ml-1 or g-1) were higher than in other tissues sampled at slaughter. At slaughter there was evidence of residue accumulation in pigmented eye tissue (33.1 +/- 6.1 pmol g-1) and in white (13.4 +/- 3.4 pmol g-1) and black hair (28.9 +/- 8.9 pmol g-1). Evaluation of radio-HPLC profiles of urine and bile extracts generally indicated that 19NT and 19NT laurate residues were present in relatively small amounts among a complex mixture of metabolites. GC-MS analysis of glucuronidase-hydrolysed bile extracts indicated that the major metabolites were 5 beta-estrane-3 alpha, 17 alpha-diol, 5 alpha-estrane-3 beta, 17 alpha-diol. 5 alpha-estran-3 alpha-ol-17-one (norandrosterone) and estra-1,3,5(10)-triene-3,17 alpha-diol (17 alpha-estradiol).

Anabolic Agents↗
PubMed1997

Function of the Escherichia coli msbB gene, a multicopy suppressor of htrB knockouts, in the acylation of lipid A. Acylation by MsbB follows laurate incorporation by HtrB.

Overexpression of the Escherichia coli msbB gene on high copy plasmids suppresses the temperature-sensitive growth associated with mutations in the htrB gene. htrB encodes the lauroyl transferase of lipid A biosynthesis that acylates the intermediate (Kdo)2-lipid IVA (Brozek, K. A., and Raetz, C. R. H. (1990) J. Biol. Chem. 265, 15410-15417). Since msbB displays 27.5% identity and 42.2% similarity to htrB, we explored the possibility that msbB encodes a related acyltransferase. In contrast to htrB, extracts of strains with insertion mutations in msbB are not defective in transferring laurate from lauroyl acyl carrier protein to (Kdo)2-lipid IVA. However, extracts of msbB mutants do not efficiently acylate the product formed by HtrB, designated (Kdo)2-(lauroyl)-lipid IVA. Extracts of strains harboring msbB+ bearing plasmids acylate (Kdo)2-(lauroyl)-lipid IVA very rapidly compared with wild type. We solubilized and partially purified MsbB from an overproducing strain, lacking HtrB. MsbB transfers myristate or laurate, activated on ACP, to (Kdo)2-(lauroyl)-lipid IVA. Decanoyl, palmitoyl, palmitoleoyl, and (R)-3-hydroxymyristoyl-ACP are poor acyl donors. MsbB acylates (Kdo)2-(lauroyl)-lipid IVA about 100 times faster than (Kdo)2-lipid IVA. The slow, but measurable, rate whereby MsbB acts on (Kdo)2-lipid IVA may explain why overexpression of MsbB suppresses the temperature-sensitive phenotype of htrB mutations. Presumably, the acyloxyacyl group generated by excess MsbB substitutes for the one normally formed by HtrB.

Acylation↗
PubMed1985

Seasonal change and sex difference in laurate hydroxylase activity in frog liver microsomes.

The content of cytochrome P-450 and the specific activity of laurate hydroxylation have been measured at monthly intervals through the year in liver microsomes of males and females of Japanese bullfrog, Rana catesbeiana. The specific activity, based on microsomal protein or cytochrome P-450 of both sexes was higher in spring (April-May) than in autumn (October-November) and the difference was statistically significant. However, in males the content of the cytochrome P-450 in the spring was almost the same level as in the autumn and it was rather lower in the spring than in the autumn in females. These suggest that the cytochrome P-450 species catalyzing laurate hydroxylation increased specifically in the spring. The specific activity (based on cytochrome P-450) in males was significantly higher than that in females in spring (April-May) or autumn (October-November).

Animals↗