Lipids from Sugar Beet in Relation to the Preparation and Properties of (Sodium + Potassium)-Activated Adenosine Triphosphatases

Field grown leaves of sugar beet contained 0.89% of their fresh weight as chloroform : methanol 1 :2 extractable material, whereas climate chamber grown material contained 0.34, 0.15, and 0.16% in leaves, stalks, and roots respectively. A striking feature was the high proportion of sulfolipid: 7% of the total extractable of the field grown leaves, 19.5, 28.0, and 37.0% of the total extractable of respectively leaves, stalks, and roots from the climate chamber grown material. Among the fatty acids, all chain lengths from C₁₂ to C₂₈ were found, except only C₁₇ and C₁₉—Exceptionally high contents of fatty acids with a chain length of C₂₆ or C₂₈ were noted in some cases. The 2500–20,000 g fraction of root homogenates contained 19% of the total root lipids. Almost all of the phosphatidyl choline and about half of the phosphatidyl ethanolamine, but only 5% of the sulfolipid followed the fraction. A fractionation of conjugate lipid types was evident, with a loss of 18/2 and 18/3 conjugates, and with an increase in the proportions of 16/0 and, possibly, of the long-chain (around C₂₆) conjugates. The unspecific ATPase activity of the 2500–20,000 g fraction was rendered specific for (Na⁺+ K⁺) stimulation by treatment with 0.1% deoxycholate for 1 hour. This induced a more than 2-fold swelling of the preparation. About half of its total lipids were lost. Again, this loss was a fractional one, so that the phosphatidyl choline lost its long-chain (about C₂₆) fatty acid conjugate while the short to medium length chain conjugates remained; whereas the reverse was the case with the sulfolipid. The ATPase activity of the 2500–20,000 g fraction was destroyed by a 24 hour treatment with deoxycholate. As compared with the 1 hour treatment, the preparation lost about 20% both of its volume and of its chloroform : methanol extractable material. The quantitatively dominating loss was found in the (pigment + neutral fat) fraction. The monogalactosyl diglyceride, the phosphatidyl inositol, and a strongly acidic unknown fraction survived the deoxycholate treatments comparatively well. In the sulfolipid the fractionating effect of the prolonged deoxycholate treatment expressed itself as a loss mainly from the long-chain (about C₂₆) fatty acid conjugate. The (Na⁺+ K⁺) stimulation of the ATPase function of the particulate preparation is thus correlated with the balance between the long-chain (about C₂₆) fatty acid conjugates of zwitterionic phosphatidyl choline and anionic sulfolipid. This is of theoretical interest, since it indicates that the specific lipid composition under appropriate conditions may influence the charge and conformation of a lipoprotein complex, thereby determining its functional capacities.     

Lipid Composition of Whole Roots and of Ca2+, Mg2+-activated Adenosine Triphosphatases from Wheat and Oat as Related to Mineral Nutrition

Lipid composition of whole roots of wheat (Triticum vulgare Vill. cv. Svenno Spring Wheat) and oat (Avena sativa L. cv. Brighton) and of cell wall fractions, mitochondrial fractions and microsomal fractions of these roots were studied. Lipid composition depended upon the level of mineral nutrition. In wheat total phospholipids, phosphatidyl choline and sulfolipid content was highest in the roots grown at the higher salt concentration, while the reverse was true for oat roots. In both species glycolipid and sterol content was lower in the high salt roots, at the same time as higher proportions of them were built into the microsomal fraction. Phosphatidyl choline content of the wheat root membrane fractions increased with the salt level, while the opposite occurred in the oat roots. The phosphatidyl choline content may be correlated with the (Ca²⁺, Mg²⁺)-stimulated ATPase activity.     

The Polyunsaturated Fatty Acids of Marine and Freshwater Cryptomonads1

SYNOPSIS Fatty acids were examined of photosynthetic and non-photosynthetic marine and freshwater cryptomonads cultured as photoauxotrophs, photoheterotrophs and heterotrophs at various incubation temperatures and constant light intensity. Photo-synthetic marine and freshwater forms contained octadecatrienoic, octadecatetraenoic, eicosapentaenoic and docosahexaenoic (all-cis, ω3 acids) as the major polyunsaturates, and a freshwater heterotroph contained mostly the octadecatrienoic acid. The polar lipids of a marine, photosynthetic form, Cryptomonas sp., included the usual thylakoid membrane lipids of the chloroplasts of eukaryotic, photosynthetic cells: galactosyl diglycerides, phosphatidyl glycerol and a sulfolipid. Also present were 2 choline-containing phospholipids: phosphatidyl choline and an unknown. Ninhydrin-positive and inositol-containing lipids were not detected. Octadecatetraenoic acid comprised 75% of the total fatty acids of the monogalactosyl diglyceride fraction. The phosphatidyl glycerol was acylated mostly by ω13 trans-hexadecaenoic acid and the eicosapentaenoic acid. Evolutionary relationships of cryptomonads as mirrored in lipid composition are discussed.     

Control of the potassium ion-stimulated adenosine triphosphatase of pig gastric microsomes: effects of lipid environment and the endogenous activator

The K⁺-stimulated ATPase activity associated with the purified gastric microsomes from the pig gastric mucosa can be completely inactivated by treatment with 15% ethanol for 60 s at 37 °C but not at 25 °C. Sequential exposure of the microsomes to 15% ethanol at 25 and 37 °C caused the release of 2.9 and 4.3% of the total membrane phospholipids, respectively, consisting entirely of phosphatidyl choline and phosphatidyl ethanolamine. The ethanol-treated (37 °C) membrane had high basal (with Mg²⁺ as the only cation in the assay mixture) activity, which was further enhanced during reconstitution with phosphatidyl choline or phosphatidyl ethanolamine. The high basal activities could be reduced to the normal control level by assaying the enzyme in presence of the “activator protein,” partially purified from the soluble supernatant of the pig gastric cells. Phosphatidyl choline was somewhat more effective than phosphatidyl ethanolamine in the restoration of the activity of the ethanol-treated enzyme while phosphatidyl serine, phosphatidyl inositol, and sphingomyelin were without any effect. Synthetic phosphatidyl choline with various fatty acid substitutions were tested for their effectiveness in the restoration of the ethanol-inactivated enzyme. The distearoyl (18:0), dioleoyl (18:1), and dilinoleoyl (18:2) derivatives of phosphatidyl choline were almost equally effective while dipalmitoyl (16:0) phosphatidyl choline was somewhat less effective in the reconstitution process. Cholesterol appeared to interfere with phosphatidyl choline in the restoration of the activity of ethanol-treated enzyme. The fatty acid composition of phosphatidyl choline and phosphatidyl ethanolamine extracted by 15% ethanol at 37 °C was clearly different than those of the total microsome. Our data suggest that the phospholipids extracted by 15% ethanol at 37 °C are derived primarily from the immediate lipid environment of the enzyme and ATP together with Mg²⁺ and K⁺ help the partially delipidated enzyme to retain the appropriate conformation for the subsequent reconstitution. Furthermore, ethanol appears to either release or inactivate the membrane-associated activator protein, demonstrated to be essential for the K⁺-stimulated activity of the pig gastric ATPase.     

Effect of lipids on chloride and sodium transport in bean and cotton plants

This paper describes experiments on Cl transport into the roots, stem and leaves of bean plants, the roots of which have been exposed to lipids in the root solution. Monoand digalactose diglyceride strongly increased Cl transport into all plant parts, probably by transport of the glycolipids further into the plant. Phosphatidyl choline increased Cl absorption by the roots, but transport into the stem and leaves was not affected. This phospholipid was only absorbed by the root tissue. ³²P-glycerophosphoryl choline added to the root solution was readily transported and esterified as phospholipid in all plant parts. This chemical did increase Cl uptake by the roots but Cl accumulation in the leaves was reduced by as much as 40%. Phosphatidyl glycerol, phosphatidyl inositol, and sulfolipid increased Cl transport into roots, stem, and leaves, and a high mobility of ³²P-phosphatidyl glycerol was demonstrated. Generally no significant effect of the above lipids on Na transport in beans and cotton was noted except that monogalactose diglyceride did increase Na transport in cotton.     

In vivo incorporation of l-[14C]serine into phospholipids and proteins of the subcellular fractions of developing rat brain

A study was conducted on the in vivo incorporation of l -[¹⁴C]-serine into the lipids and proteins of the various subcellular fractions of the developing rat brain before and during the stage of active myelination. The total radioactivity in the various fractions at 12 days of age was higher than that at 3 days, while the radioactive specific activity was reversed. The specific activities of the proteins and lipids were higher at 3 days of age with the exception of the subcellular fraction containing myelin. At both ages the lipids of the various cellular fractions had similar specific activities, a finding that suggests a common source for lipid biosynthesis. Incorporation of radioactivity into the various phospholipids was in the following order: phosphatidyl serine > phosphatidyl ethanolamine > phosphatidal serine > sphingomyelin and phosphatidyl choline. Of all the phospholipids, the plasmalogens increased most in total radioactivity during the period when meylination was most active. Serine-containing phospholipids appear to be most tightly bound to proteins. The brain mitochrondrial fraction contained most of the phosphatidyl serine decarboxylase activity with some activity in the nuclei. Biosynthesis of phosphatdyil ethanolamine through decarboxylation of phosphatidyl serine could take place in rat brain. Four unidentified radioactive metabolites were found in the acid-soluble fraction in addition to l -[¹⁴C]serine.     

Phosphatidyl inositol-specific phospholipase C from Clostridium novyi type A

From the culture broth of Clostridium novyi type A, phosphatidyl inositol-specific phospholipase C was separated from the major part of phospholipase C (γ-toxin) which hydrolyzes phosphatidyl choline, phosphatidyl ethanolamine, and sphingomyelin. Sodium deoxycholate stimulated the activity of phosphatidyl inositol phospholipase C. The concentration of sodium deoxycholate for maximal stimulation was 0.2% with 2 mm phosphatidyl inositol. Divalent cations (Mg²⁺, Ca²⁺, and Zn²⁺) were rather inhibitory above 10^?3m. Phosphatidyl inositol phospholipase C was not inhibited by EDTA or o-phenanthroline. When phosphatidyl inositol phospholipase C was incubated with rat liver slices, not only alkaline phosphatase but also 5′-nucleotidase was liberated into the soluble fraction.     

Lipids of Chlamydomonas reinhardi under different growth conditions

Photo-, mixo- and heterotrophically grown cultures of Chlamydomonas reinhardi (wild type ss and 2 streptomycin-resistant mutants sr₃ and sr₃₅) have been analyzed for lipids and fatty acids. Ether-soluble lipids, chlorophyll, monogalactosyl diglyceride, digalactosyl diglyceride, sulfolipid, phosphatidyl ethanolamine, phosphatidyl choline, phosphatidyl glycerol and the relative amounts of fatty acids in total and individual lipids have been determined. The lipid and fatty acid compositions are very similar in the 3 strains and are not affected by the mutations. Fatty acids belong exclusively to the C₁₆ and C₁₈ series, 16:0, 16:4, 18:1, 18:2, 18:3 (6,9,12) and 18:3 (9,12,15) comprising about 90% of the total. 18:3 (6,9,12) is concentrated in phosphatidyl ethanolamine. In streptomycin-bleached sr₃ cells, ether-soluble lipids increase from 7 to 11% of dry weight on greening, mostly due to synthesis of monogalactosyl diglyceride and chlorophyll. Monogalactosyl diglyceride of bleached cells exhibits the same fatty acid pattern before and after greening.     

Cyclopropane Fatty acids in relation to earliness in spring and drought tolerance in plants

Long chain cyclopropane fatty acids were observed in the sulfolipid fraction extracted from leaves of the early spring plants Galanthus nivalis L. and Anthriscus silvestris L. (Hoffm.). The content of cyclopropane fatty acids with 25 carbon atoms appeared to be clearly correlated with earliness in spring, and it ranged from 68% (G. nivalis L., snow drop) to 0.5% (wheat). Several long chain cyclopropane fatty acids were found in the drought-tolerant Corynephorus canescens (L.) P.B., exclusively in the phosphatidyl choline fraction.     

Influence of Calcium on Alleviating NaCl-Induced Injury Effects in Wheat Seedlings

Wheat seedlings (Tritium aestivum "No. 1 Yuyuan") with 3 leaves were transplanted to 1/2 strangth Hoagland nutrient solution containing 100 mmol/L NaCl and supplemented with different concentrations of CaCI2, which were mode isosmotic by adding polyethylene glycol (PEG) and aerated by pump. Results showed that the Na+ content of shoots and roots, relative leaf expansion rate, plasma membrane permeability, the levels of membrane lipid superoxidation and the molar percentage of monogalacrosyl diglyceride(MGDG), digalactosyl diglyceride(DGDG) phosphatidyl choline(PC) and phosphatidyl ethanolamine(PE) in membrane lipids of roots increased, the plant dry weight, K+ content, SOD activity and the molar percentage of phosphatidic acid(PA), phospatidyl inositol (PI), phosphatidyl glycerol(PG) and polyphosphoglyceric acid(PPG) decreased in roots. There was no change in sulfolipid(SL). However, the above mentioned salt injury effects were all alleviated by the different Na+/Ca2+ ratios. The maximum alleviation of salt injury effect was at Na+/Ca2+ ratio of I0. As three kinds of free radical scavengers were used to pretreat wheat seedlings prior to NaC1 treatment the malondialdehyde(MDA) content decreased unanimously, but increased with SOD inhibitor sodium diethyldithiocarbamate (DDTC) pretreatment to wheat seedlings. Obviously, the salt injury effects induced by NaC1 was relatied to the extent of superoxidation of membrane [ipids and also to the composkion of membrane of Ca2+ on lipids including their fatty acids as well. On the other hand, the alleviating effect of Ca2+ on NaC1 induced injury in wheat seedlings was also in relation to them.     

ASSEMBLY OF LIPIDS INTO MEMBRANES IN ACANTHAMOEBA PALESTINENSIS : I. Observations on the Specificity and Stability of Choline-14C and Glycerol-3H as Labels for Membrane Phospholipids

In order to determine the feasibility of using radioactive precursors as markers for membrane phospholipids in Acanthamoeba palestinensis, the characteristics of phospholipids labeled with choline-¹⁴C and glycerol-³H were examined. Choline-¹⁴C was found to be a specific label for phosphatidyl choline. There was a turnover of the radioactive moiety of phosphatidyl choline at a rate that varied with the concentration of nonradioactive choline added to the growth medium. Radioactivity was lost from labeled phosphatidyl choline into the acid-soluble intracellular pool and from the pool into the extracellular medium. This loss of radioactivity from cells leveled off and an equilibrium was reached between the label in the cells and in the medium. Radioactive choline was incorporated into phosphatidyl choline by cell-free microsomal suspensions. This incorporation leveled off with the attainment of an equilibrium between the choline-¹⁴C in the reaction mixture and the choline-¹⁴C moiety of phosphatidyl choline in the microsomal membranes. Therefore, a choline exchange reaction may occur in cell-free membranes, as well as living A. palestinensis. In contrast to choline-¹⁴C, the apparent turnover of glycerol-³H-labeled phospholipids was not affected by large concentrations of nonradioactive choline or glycerol in the medium. The radioactivity in lipids labeled with glycerol-³H consisted of 33% neutral lipids and 67% phospholipids. Phospholipids labeled with glycerol-³H turned over slowly, with a concomitant increase in the percentage of label in neutral lipids, indicating a conversion of phospholipids to neutral lipids. Because most (~96%) of the glycerol-³H recovered from microsomal membranes was in phospholipids, whereas only a minor component (~2%) of the glycerol-³H was in the phospholipids isolated from nonmembrane lipids, glycerol-³H was judged to be a specific marker for membrane phospholipids.     

Effects of pyridoxal phosphate treatment on the (Na + K)-ATPase

Reaction of a dog kidney (Na + K)-ATPase with pyridoxal phosphate, followed by borohydride reduction, reduced the catalytic activity when measured subsequently. The time course of inactivation did not follow a first-order process, and certain characteristics of the residual enzymatic activity were modified. Moreover, various catalytic activities were diminished differently: Na-ATPase activity was largely spared, K-phosphatase activity was diminished only by half that of the (Na + K)-ATPase, whereas (Na + K)-CTPase and Na-CTPase activities were diminished more. ATP, ADP, CTP, nitrophenyl phosphate, and P_i all protected against inactivation. Increasing salt concentrations increased inactivation, but KCl slowed and NaCl hastened inactivation when compared with choline chloride. Occupancy of certain substrate or cation sites seemed more crucial than selection of conformational states. For the residual (Na + K)-ATPase activity theK _0.5 for K⁺ was lower and theK _0.5 for Na⁺ higher, while the sensitivities to ouabain, oligomycin, and dimethylsulfoxide were diminished; for the residual K-phosphatase activity theK _0.5 for K⁺ was unchanged, the sensitivity to ouabain and oligomycin diminished, but the stimulation by dimethylsulfoxide increased. These properties cannot be wholly accommodated by assuming merely shifts toward either of the two major enzyme conformations.     

Lipid composition of cyanidium

The major lipids in Cyanidium caldarium Geitler are monogalactosyl diglyceride, digalactosyl diglyceride, plant sulfolipid, lecithin, phosphatidyl glycerol, phosphatidyl inositol, and phosphatidyl ethanolamine. Fatty acid composition varies appreciably among the lipids, but the major ones are palmitic acid, oleic acid, linoleic acid, and moderate amounts of stearic acid. Trace amounts of other acids in the C₁₄ to C₂₀ range were also present. Moderate amounts of linolenic acid were found in two strains, but not in a third. The proportion of saturated acid is relatively high in all lipids ranging from about a third in monogalactosyl diglyceride to three-fourths in sulfolipid. This may be a result of the high growth temperature. Lipases forming lysosulfolipid, and lysophosphatidyl glycerol are active in ruptured cells; galactolipid is degraded with loss of both acyl residues. Thus the lipid and fatty acid composition of Cyanidium more closely resembles that of green algae than that of the blue-green algae, although there are differences of possible phylogenetic interest.     

In vivo covalent binding of 14CCl4 metabolites in liver microsomal lipids

Covalently bound ¹⁴C from ¹⁴CCl₄ is preferentially localized in the lipids of hepatic microsomes of rats within 15 min. Label was recovered in all classes of lipids isolated from the microsomal lipid extract by diethylaminoethyl column chromatography. Among phospholipids, specific activity was the highest in the fraction containing phosphatidyl serine and lowest in phosphatidyl choline. Cholesterol esters had more than ten times the specific activity of cholesterol.     

Coupled Na+ -K+ transport in vesicles containing a purified (NaK)-ATPase and only phosphatidyl choline.

Endogenous phospholipids of a purified (NaK)-ATPase were displaced by exogenous phosphatidyl choline. If vesicles were made from phosphatidyl choline and enzyme containing only phosphatidyl choline, coupled Na⁺K⁺ transport could be demonstrated. This transport was inhibitable by ouabain. Therefore, the number of components necessary for Na⁺K⁺ transport has been reduced to the purified (NaK)-ATPase and one phospholipid.     

Lipid metabolism in chromoplast membranes from the daffodil: Glycosylation and acylation

The non-photosynthetic chromoplast membranes from the corona ofNarcissus pseudonarcissus L. were investigated for their lipid synthetic capabilities. The following activities were detected: galactosylation of diacylglycerol and galactosydiacylglycerols, glycosylation of sterols, acylation of monogalactosyldiacylglycerol and steryl glycosides from an unknown endogenous donor, acylation of phospholipids from acyl-CoA, and acylation of phosphatidyl inositol from phosphatidyl choline. Furthermore, activities of an acyl thioesterase, a sugar epimerase, and a phospholipase A₂ were measured.Abbreviations MGDG monogalactosyldiacylglycerol - DGDG digalactosyldiacylglycerol - TGDG tri-and tetragalactosyldiacylglycerol - SG steryl glycoside - SL sulfolipid - ACP acyl carrier protein     

Hormonal Regulation of Ca2+ Stimulated K+ Influx and Ca2+, K+- ATPase in Rice Roots: in vivo and in vitro Effects of Auxins and Reconstitution of the ATPase

The role of natural and synthetic auxins in regulation of ion transport and ATPase activity was studied in rice roots (Oryza sativa L. cv. Dunghan Shah). In vivo treatment of seedlings with 2,4-dichlorophenoxyacetic acid at 2 × 10^?6M for a short period enhanced subsequent Ca²⁺ stimulated K⁺ influx and ATPase activity, while a longer treatment diminished both K⁺ influx and ATPase activity. Indoleacetic acid at 10^?10–10^?8M induced ATPase activity. In in vitro experiments both 2,4-dichloro phenoxyacetic acid and indoleacetic acid (10^?10–10^?8M) stimulated Ca²⁺, K⁺-ATPase activity of a plasmalemma rich micro somal fraction from the roots. Acetone extracted ATPase preparations lost their activity. The enzyme regained its activity and its sensitivity towards ions (Ca²⁺+ K⁺) when reconstituted with phosphatidyl choline. Addition of auxins also indicated that the presence of the lipid was necessary in the interaction between the ATPase and auxins. Auxins and ions probably interact with the intact ATPase lipoprotein complex, which may possess a receptor site for the auxins, possibly as a sub unit.     

The effect of divalent cations on Na+ tolerance in Charophytes. I: Char a buckellii

Abstract The comparative Na⁺ tolerance of Chora buckellii cultured in freshwater (FW) or artificial Waldsea water (AWW, which contains about 110 mol m^?3 each Na ⁺, Mg²⁺, Cl^? and SO^2-₄ was tested with respect to the external Na⁺ to Ca²⁺ ratio (Na: Ca). Fifty per cent of FW cells subjected to 70 mol m^?3 NaCl, which raised Na:Ca from 10: 1 to 700: 1 and the external osmotic pressure from 0.024 to 0.402 MPa, died within 6 d. Death was associated with the loss of Na/K selectivity, H⁺ -pump activity and turgor. Restoration of Na:Ca to 10:1 in high Na⁺ medium with CaCl₂ ensured 100% survival and maintained H⁺-pump activity and Na/K selectivity of FW cells. Turgor was regulated within 3 d with net uptake of Na ⁺, K⁺ and Cl^? in the vacuolc. Mg²⁺ was not as effective as Ca²⁺ in enhancing survival or maintaining H⁺ -pump activity and Na/K selectivity of FW cells in the presence of elevated Na⁺. However, turgor was regulated within 3 d by accumulation of Cl^? and an unknown cation in the vacuole. All AWW cells subjected to an increase of 70 mol m ^?3 NaCl, which raised Na: Ca from 16:1 to 25: 1 and the external osmotic pressure from 0.915 to 1.22 MPa, survived and maintained H ⁺ -pump activity. Turgor was regulated within 6d by accumulating Na ⁺, K⁺ and Cl^? in the vacuole. All AWW cells subjected to 70molm^?3 NaCl in a medium in which Na:Ca was equal to 700:1 survived and maintained H ⁺ -pump activity, but showed loss of Na/K selectivity. Turgor was regulated with an unknown osmoticum(a) within 6 d.     

Hepatic Subcellular Fractions Lipids in Rats Fed Millet (Sorghum vulgarie) at Different Protein Levels

Effect of feeding defatted millet (Sorghum vulgarie) flour at 5, 10 and 14.5% protein levels respectively for six weeks has been studied on rat liver mitochondrial, microsomal and supernatant fractions total lipids, cholesterol, triglycerides, total phospholipids, phosphatidyl choline and phosphatidyl ethanolamine. The results have been compared with rats fed casein at 10% level for the same period. The metabolism of liver subcellular fractions lipids of millet diet and casein diet fed rats has been studied by the incorporation of acetate-1-¹⁴C and . A significant increase in mitochondrial triglycerides of rats fed millet diet at 5 and 10% protein level, in microsomes of rats fed millet diet at 5, 10 and 15% protein levels and in supernatant fractions of rats fed millet diet at 5 and 15% protein levels was observed. A significant increase in total cholesterol in mitochondria and microsomes and a significant decrease in supernatant fraction of rats fed millet diet at 10% protein level was observed. A significant increase in mitochondrial total phospholipids, phosphatidyl choline and phosphatidyl ethanolamine in rats fed millet diet at 10% protein level and a decrease in these in rats fed millet diet at 5 per cent protein level was observed. In microsomes total phospholipids were increased in rats millet diet at 10% protein level and phosphatidyl choline was increased in rats fed millet diet at 15% protein level. Total phospholipids, phosphatidyl choline and phosphatidyl ethanolamine were significantly reduced in the supernatant fraction of rats fed millet at 10% protein level.

Incorporation of acetate-1-¹⁴C into nonsaponifiable fraction of mitochondria, microsomes and supernatant fractions of rats fed millet diet at 5 and 15 % protein levels was significantly greater, and in saponifiable fractions of the above subcellular fractions was greater in rats fed millet diet at 5 per cent protein level. The specific activity (counts/min/mg) of free cholesterol in mitochondria, microsomes and supernatant fractions of millet diet fed rats was significantly greater, whereas the specific activity of triglycerides was not significantly different from the controls. The acetate-1-¹⁴C specific activity of phosphatidyl choline and phosphatidyl ethanolamine was significantly greater in all the above subcellular fractions of millet diet fed rats (except of phosphatidyl choline in rats fed millet diet at 5 % protein level). The specific activities of phosphatidyl choline were significantly greater in mitochondria of rats fed millet diet at 5 % protein level and of phosphatidyl choline and phosphatidyl ethanolamine in microsomes and supernatant fractions of rats fed millet diet at 5 and 15% protein levels. The specific activities of phosphatidyl choline were significantly decreased in mitochondria and microsomes of rats fed millet diet at 10% protein level. The total acetate-1-¹⁴C activities (counts/min/g equivalent wet liver) of free and esterified cholesterol triglycerides, phosphatidyl choline and phosphatidyl ethanolamine showed that their synthesis from acetate-1-¹⁴C was either enhanced in millet diet fed rats or was comparable to the controls. The total activity of (counts/min/g equivalent wet liver) into phosphatidyl choline and phosphatidyl ethanolamine showed that their synthesis was decreased in microsomes of rats fed millet diet at 10% protein level, increased in rats fed millet diet at 5 and 15% protein levels.     

Mechanism of lipid activation of Na,K, Mg-activated adenosine triphosphatase and K,Mg-activated phosphatase of bovine cerebral cortex

Summary Na⁺, K⁺, Mg⁺⁺-activated adenosine triphosphatase and K⁺, Mg⁺⁺-activatedp-nitrophenyl phosphatase prepared from a membrane fraction of bovine cerebral cortex were studied with regard to the manner of their activation by phospholipids, using phosphatidyl serine, lysolecithin, monodecyl and didecyl phosphates. The kinetic and chromatographic studies suggested the following. (1) When the enzyme proteins bind the phospholipids in a proper ratio, they attain the optimum activation. (2) The binding causes a simple conversion of the enzymes from an inactive form to a fully activated form. (3) The lipids in both micellar form and molecular dispersion activate the enzymes. (4) Of the proteins contained in the enzyme preparation, only a group of proteins possessing the ATPase and the phosphatase activities bind phospholipids, and the amount of the bound lipids is limited.