[Conversion of beta-carotene and some beta-apocarotinoids under the effect of substances from the intestinal mucosa]. / Issledovanie prevrashcheniia beta-karotina i nekotorykh beta-apokarotinolov pod deistviem preparatov mukoidal'nogo sloia kishechnika.

Products of cleavage of beta-carotene and certain apocarotenoids (beta-apo-4', 8', 10', and 12'-carotenols and citranaxanthol) were studied, and the dynamics of their generation in the presence of an enzyme preparation isolated from rabbit intestinal mucosa was determined. The data suggest that metabolism of beta-apocarotenols involves the production of retinal and beta-apo-14'-carotenal mediated by enzymes different from beta-carotene-15,15'-dioxygenase, which converts beta-carotene to retinal. A scheme of metabolic conversion of beta-carotene is discussed.

Enzymatic oxidation of beta-apo-8'-carotenol to beta-apo-14'-carotenal by an enzyme different from beta-carotene-15,15'-dioxygenase.

Extracts of rat and rabbit intestinal mucosa were fractionated with ammonium sulfate. The precipitate contained beta-apocarotenoid-14',13'-dioxygenase (ADO) activity. beta-Apo-14'-carotenal was found to be the product of enzymatic cleavage of beta-apo-8'-carotenol. Activities of ADO and beta-carotene-15,15'-dioxygenase (CDO) were detected in the presence of thiols and were inactivated by 1,10-phenanthroline. Optimal pH values were 7.0 for ADO and 8.0 for CDO. Heating at 52 degrees C inhibited ADO by 70% and produced no effect on CDO. ADO activity was maximal in the presence of sodium cholate or 3-[(3-cholamidopropyl)-dimethyl-ammonio]-1-propanesulfonate (CHAPS). Sodium dodecylsulfate was required for maximal CDO activity. Proteins with ADO activity were not retained by phenyl-Sepharose CL-4B. CDO activity was eluted from columns only in the presence of detergents. The data suggest that the enzymes that catalyze the oxidative cleavage of beta-carotene to yield retinal are different from those that cleave beta-apo-8'-carotenol to yield beta-apo-14'-carotenal.

Stabilization and competitive inhibition of beta-carotene 15,15'-dioxygenase by carotenoids.

Carotenoids stabilize beta-carotene 15,15'-dioxygenase (CDO) during the isolation of the enzyme from the rabbit small intestinal mucosa using a thiol protector and protease inhibitors and in the course of the enzyme purification. The inhibition of CDO by lycopene, lutein and astaxanthin is competitive. Carotenoids partly protect CDO from the action of both iodacetate and trypsin due to enzyme-pseudosubstrate interaction.

[The character of the interaction of beta-carotene-15,15'-dioxygenase from rabbit small intestine with lycopene, 15,15'-dehydro-beta-carotene, lutein, and astaxanthine]. / O kharaktere vzaimodeistviia beta-karotin-15,15'-dioksigenazy iz tonkogo kishechnika krolika s likopinom, 15,15'-degidro-beta-karotinom, liuteinom i astaksantinom.

Interaction of rabbit small intestine mucosa beta-carotene 15,15'-dioxygenase with lycopene, 15,15'-dehydro-beta-carotene, lutein and astaxanthine is unaccompanied by the formation of products of enzymatic cleavage of the central double bond of these carotenoid molecules. Apo-carotenoids of lutein and lycopene are formed by nonenzymatic oxidation. Lycopene and 15,15'-dehydro-beta-carotene competitively inhibit the enzymatic oxidation of beta-carotene. Inhibition of the enzyme conversion by lutein and astaxanthin is less strong, being of a competitive-noncompetitive type. Enzymatic formation of retinal from beta-carotene depends on the accessibility of substrate molecules.

[Properties of beta-carotene-15,15'-dioxygenase, stabilized during purification with lutein and dithiothreitol]. / Svoistva beta-karotin-15,15'-dioksigenazy, stabilirzirovannoi v protsesse vydeleniia liutenom i ditiotreitolom.

Preparations of beta-carotene 15,15'-dioxygenase (EC 1.13.11.21) obtained with or without lutein and dithiothreitol (DTT) as stabilizers display similar properties. The stabilized preparation has an apparent Km of 17 microM and Vmax of 2.8 nM/h/mg of protein, a pH optimum of 8.1, is sensitive to SH-agents and is activated by Fe2+, DTT or glutathione used at optimal concentrations of 0.5 mM, 2 mM, and 5 mM respectively. At DTT concentration above 2 mM the enzyme activity decreases drastically, which testifies to the importance of maintaining the thiol and disulphide group ratio in the protein molecule at an optimal level. At 4 mM Fe2+ there occurs a nonenzymatic formation of apo-carotenals; however, retinal is formed only after addition of commensurate amounts of thiol compounds. The enzyme activity depends on the ionic strength of the incubation medium, the maximal effect being observed with 0.4 M K-phosphate buffer. Substitution of phosphate for Cl- partly inhibits the enzyme. The optimal temperature for this reaction is 45 degrees. A simultaneous use of optimal incubation parameters (2 mM DTT, 0.4 M K-phosphate buffer pH 8.1 and 45 degrees C) increases the retinal yield 2.5-fold against control.

[Enzymatic conversion of torulene and torularhodine into retinal]. / Fermentativnoe prevrashchenie torulina i torularodina v retinal'.

The enzymatic conversion of torulene to retinal is demonstrated in in vitro tests using beta-carotene 15,15'-dioxygenase (EC 1.13.11.21) from the rabbit small intestine mucosa. This is the first evidence for the potent vitamin A activity of torulene. Little amounts of retinal also formed from methyl ester of torularhodin and from torularhodin.

[Stabilization and protection of an enzymatic system, participating in the transformation of beta-carotene into retinal, during its isolation]. / Stabilizatsiia i zashchita fermentnoi sistemy, uchastvuiushchei v orevrasgcgebuu v beta-karotina v retinal', pri ee vydelenii.

The authors studied the effect of dithiothreitol (DTT), carotenoids and protease inhibitors on stabilization and protection of the enzyme catalysing the conversion of beta-carotene into retinal during the enzyme isolation from the rabbit small intestine. The addition of 1 mM DTT into the homogenization mixture increased the activity of the enzyme 5 times compared with control. The additional introduction of 0.7 mg/ml soybean trypsin inhibitor or 2.10(-4) M phenylmethylsulfonyl fluoride increased the enzyme activity 2.1 and 1.2 times, respectively. Lutein, beta-carotene and lycopene at a concentration of 10 mg/ml increased the enzyme activity 2.1, 1.9 and 1.6 times respectively. The effects of DTT, lutein and the protease inhibitor depended on their concentrations and was of an independent additive character. The maximum activity of the isolated enzyme exceeded the control without DTT 15 times.

[Effect of vitamin B12 on carnitine synthesis in the body of rats]. / Vliianie vitamina B12 na sintez karnitina v organizme krys.

The effect of vitamin B12 on carnitine metabolism in rats has been investigated. The injection of coenzyme B12 into male rats has been shown to result in the increase of carnitine in liver. The dynamics of this process and its dependence on the age of rats have been studied. A possible mechanism of anabolic action of vitamin B12 and carnitine is under discussion.

[Dynamics of vitamin A metabolism in the blood and semen of karakul ram sires]. / Dinamika obmena vitamina A v krovi i semeni baranov-proizvoditelei karakul'skoi porody.

Dynamics of vitamin A turnover in the blood and semen of astrakhan ram-sires was being studied for determining the ways of its transport to mature sperms. By means of high pressure liquid chromatography it was found that concentrations of retinol in the blood and retinyl palmitate in the semen of rams, suffering from hypovitaminosis A, rose simultaneously during the first 24 hours after feeding the animals with labelled retinol. According to the data on the specific activity of labelled vitamin A in the blood and semen a significant portion of the vitamin was transfered into the semen from the blood together with the secretions of epididymis and/or another sexual glands. The role of vitamin A in epididymal sperm maturation is discussed. A more prolonged increase of vitamin A levels in the blood and semen of the animals under study was achieved after double feeding of each animal with 60 mg of vitamin A.

[Antifungal and antimicrobial activity of beta-ionone and vitamin A derivatives]. / Antifungal'naia i antimikrobnaia aktivnost' nekotorykh proizvodnykh beta-ionona i vitamina A.

The antifungal and antimicrobic activity of some derivatives of beta-ionon and vitamin A was studied. These compounds (citral, pseudo-ionon. beta-ionon aldehyde C14, ketone C18 and its derivatives--4,18-diketone, alcohol C18, semicarbazide ketone C18), as well as vitamin A and its derivatives--retinal, acetate, retinoic acid--differ in composition, structure and substituents of C-atoms in beta-ionon ring and in polyenoic chain. Fusarium solani, Botrytis cenerea and Verticillum dahliae II, race 447 were used as test organisms when studying the antifungal activity. When studying the antimicrobic activity, ketone C18 and alcohol C18 were tested using the museum strains Staphylococcus aureus 209 P, hemolytic Streptococcus pyogenes FF-38, Streptococcus sp. TOM-1606, Micrococcus luteus 2665, as well as the strains Staphylococcus aureus isolated from pyoderma patients. The antifungal activity was determined by inhibition of spore germination, and the antimicrobic activity--by the value of areas of growth inhibition of the test organisms on the agar medium. All the compounds mentioned above possessed the antifungal activity against all the phytopathogenes used. The degree of this activity depends on the composition and structure of both the cyclic part and polyenoic chain. on the number of conjugated unsaturations, substituents and end groups of C-atom. Ketone C18 is the most active one. It inhibits spore germination by 100-94% at concentrations ranging from 0.05 to 0.005% and 24 h exposure, and by 100% at the concentration of 0.1% and 72 h exposure. Alcohol C18 possesses almost the same antifungul activity.(ABSTRACT TRUNCATED AT 250 WORDS)

[Synthesis of retinyl phosphate, its physico-chemical properties and biological activity]. / Sintez retinilfosfata, ego fiziko-khimicheskie svoistva i biologicheskaia aktivnost'.

Retinyl phosphate (RP) has been synthesized from retinol (R), using phosphodimorpholine chloride (PDMC) or POCl3. A method for isolating and purifying RP from the reaction mixture has been developed. The RP yield varies from 3 to 6% depending on the quantities of R and POCl3. The RP yield can be increased by 10--15% as a result of RP separation and rerun of the reaction. The resultant RP has an absorption maximum at 325 nm, is described by the formula C20H27PO4(NH4)2 and distributed between equal volumes of diethyl ester and 20% aqueous methanol at a ratio of 1:1. RP is alkaline-resistant and rapidly transforms into anhydroretinol (AR) in the acid medium. Eighteen hours after RP administration into the caudal vein or parenterally retinyl palmitate and R are accumulated in the liver of A-avitaminous rats.

[Ketometabolite of vitamine A, its structure and enzymatic transformation]. / Ketometabolit vitamina A, ego struktura i énzimaticheskie prevrashcheniia

The structure and enzymatic transformations of vitamin A keto-metabolite isolated from the rat liver were investigated. With the aid of physico-chemical methods, using isotopes 3/ and 18O, PMR and mass-spectrometry it was demonstrated that the metabolite was an ester of 4-keto-retinol with palmitic acid. The structure of 4-keto-retinal was confirmed by the chemical synthesis and by the enzymatic production of its derivatives. Under the influence of alcohol dehydrogenase 4-keto-retinol in the presence of NAD transformed into 4-keto-retinal which was oxidized into 4-keto-retinoic acid with the participation ofaldehyde oxidase. Similar oxidative enzymatic transformations occurred with the reduced form of the metabolite--4-hydroxyretinol. All the products were characterized in detail. Metabolism of 4-keto-retinyl-palmitate in vivo is realized via the same pathway as metabolism of retinyl-palmitate. The general pattern of oxidation of beta-ionone ring in position 4 of vitamin A and carotenoids is discussed.

Studies on the metabolism of beta-carotene and apo-beta-carotenoids in rats and chickens.

(1)The relative abilities of the various fractions of rat and chicken liver to oxidize and reduce retinal and 8'-and 12'-apo-beta-carotenal were investigatjed and it has been shown that, while retinal is exclusely oxidized by the soluble fraction, the apocarotenals are mostly oxidized by the particulate fractions of the homogenate. (2) Addition of NAD+ or NADP+ markedly activated the oxidation of the apocarotenals, but not of retinal by the particulate fractions. (3) Considerable amounts of retinal and 8'-, 10'- and 12'-apo-beta-carotenal were isolated from the intestine of chickens fed beta-carotene and these apocarotenoids were conclusively identified. (4) Significant amounts of 8'-, 10'- and 12'-apo-beta-carotenoic acids were isolated from the intestine of rats given 8'-apo-beta-carotenal and these apocarotenoic acids were also conclusively identified. (5) In the light of these observations it is suggested that during conversion to vitamin A, the beta-carotene molecule is simultaneously attacked by the dioxygenase at several double bonds, the primary attack being at the central double bond and a tentative scheme for the mechanism of conversion is proposed.

[Detection of retinaldehyde in mouse liver]. / Obnaruzhenie retinal'degida v pecheni myshi]

Vitamin A metabolites were studied in the liver of white mice, hamsters, guinea-pigs and rabbits after a single administration of retinyl acetate per os. In addition to retinol and retinyl palmitate, the mouse showed retinaldehyde which accumulated in the liver in the maximum concentration 3 hours later after the vitamin administration. Retinaldehyde isolated on aluminium oxide by means of TCA was examined with respect to absorption spectra in the UV-light, NaBH4 reduction with subsequent isolation of anhydrovitamin A from the reduced product as well as to absorption peaks in reactions with SbCl3 and thiobarbituric acid.