FRUCTOSE

From Big Medical Encyclopedia

FRUCTOSE (synonym: levulose, fruit sugar, fruit sugar) — a monosaccharide from group of ketohexoses, C6H1206; plays an important role in energy balance at the person and animals, is a part of vegetable polysaccharides and oligosaccharides, in a free look it is found in biological liquids of the person and animals. Phosphoric ethers F. are formed as intermediate products as a result of the metabolic transformations happening in the course of carbohydrate metabolism (see) including spirit fermentation (see), glycolysis (see), a pentozny cycle, a dark phase of photosynthesis (see), etc. Genetically caused intolerance F. is the reason of a serious hereditary illness — fruktozemiya (see).

In the nature meets D - stereo-isomer F. (see the Isomerism); it is found in fruits, fruit, nectar, honey, in blood and urine of animals (especially ruminant) and the person (at a fruit and children contents F. above, than at adults), in amniotic waters (see) and transsudata (see Transudate), in seed bubbles (see) and sperm (see), where F. is the main power substrate for spermatozoa. D-fructose is a part of natural oligosaccharides — sucrose (see), raffinoses (see Oligosaccharides), etc., and also polysaccharides of fructosans — inulin, lavan, etc. (see Polysaccharides); in the form of phosphoric ethers of fruktozo-1,6-diphosphate, fruktozo-6-phosphate, etc. it is found practically in all living cells.

Free F. almost always p - D - fruktoiiranozoy, and T is., being a part of various connections — | 3-V-fruktofuranozoy. At hydrolysis of the fructosans or oligosaccharides containing F., the formed P-D - fruktofuranoza is quickly isomerized in (Z-V-fruktopira-nozu. In water solutions F. a lot of the acyclic ketonic D-fructose form contains (see Hexoses).

P-D-Fruktoza is well dissolved in water, acetone, mix of alcohol and ether, it is worse in alcohol. From water solution F. very slowly crystallizes in the form of colourless needles and leaflets. T. has sweet taste; it is 3 times more sweet than glucose (see) and sucrose is nearly 1,5 times more sweet. Slightly mu that rotirut D-fructose solution (see Mutarotation), rotates a beam of the polarized light to the left [and] ^ — — 93 ° (from here other name D-fructose — levulose), / D-fructose silt apprx. 100 °. P-D-Fruktoza can vat obrazova the osazone similar to osazone from glucose or mannose (see Osazone, z). T. about l and that on in l and va goshchen with \gives in wasps i of wasps about-nostyyu, under the influence of acids easily turns in 5-oksimetilfurfu-rol (I eat. Furfural), under the influence of D-fructose alkalis partially turns into D-glucose, and the most part collapses with a gap carbon — carbon bonds. D-Fruk-toza forms almost insoluble compound with lime and it can also be besieged by a lead acetate in ammoniac solution; (3-D-fructose is easily fermented d r about am and (with m).

Determine D-fructose by methods of a chromatography (see) and the colorimetric methods (see Colorimetry) based on education

5 oxymethylfurfurals, to-ry it is found on staining reaction with resorcin (see Selivanov test), with Anteronum, (5-indolyacetic to - that, thiobarbituric to - that, etc.

Receive P-D-fructose soft acid or enzymatic (by means of sucrose, inulaz and other enzymes) hydrolysis of fructosans or sucrose, and also alkali treatment of glucose with afterpurification F. from impurity by both other chemical and enzymatic methods.

T. food easily vsasv1vayetsya in a small bowel, at the same time its small part is phosphorylated and turns into fructose phosphate (see Phosphorylation) at and the main quantity F. in not changed look comes to a liver and it is phosphorylated there. Phosphates F. the adult has hl. obr. on synthesis of a glycogen (see) and only apprx. 13% of phosphates F. it is used for power needs of an organism with formation of an end product — lactic acid (see). In seed bubbles F. it is formed of glucose through sorbitol with participation of NADF-N and NAD +.

At hereditary intolerance F., the fruk-tozemiya which received the name and the life of the child which is shown from first weeks, at patients in response to introduction F. there are a hypoglycemia, vomiting, the dispeptic phenomena. In hard cases at patients the liver increases, jaundice, a hypoalbuminemia develops. The disease is caused by genetic defect of enzyme of the fruk-tozodifosfat-zymohexase (fruktozo-biphosphates-zymohexases, zymohexases; KF 4.1.2.13) catalyzing disintegration of fruktozo-1,6-diphosphate (or fruktozo-1-phosphate) on dihydroxyacetone-phosphate and glitseraldegid-3-phosphate (or glitseraldegid). In a human body and animals 3 isoenzymes fructose diphosphate-zymohexase are revealed: zymohexase A (muscular), zymohexase B (hepatic and renal) and zymohexase From (brain). Believe that intolerance F. is caused by genetically caused defect of zymohexase B.

At insufficiency of a ketogekso-kinase of a liver (ATP:

D-fructose 1 of phosphotransferase; KF 2.7.1.3) is broken process of education of D - fruktozo-1-phosphate from p - D - frukto-zy and the fruktozuriya after reception F develops so-called high-quality, or essential. This disease meets seldom (1:130 Ltd companies) and has no heavy forecast since D-fructose can be phosphorylated on the 6th carbon atom by means of a hexokinase (see) or fruktokinaza (KF 2.7.1.4).

Nek-ry researchers recommend to replace at a diabetes mellitus in a diet of the patient glucose with fructose, trying to bypass in such way the hexokinase block (see a diabetes mellitus). To such replacement it is necessary to belong carefully since the diabetes mellitus is caused not only insufficiency of a hexokinase; besides, introduction of large numbers F. in an organism of the patient can lead to development of acidosis (see).

Fructose in food. T. it can be considered as digestible sugar, however more slowly, than glucose, is soaked up in intestines and quicker disappears from a blood-groove. Since main quantity F., arrived with food, use F is late in a liver. in food does not cause oversaturation of blood this sugar. Unlike other sugars F. is less resistant and begins partially to change already at long boiling. It differs in bigger sweet and sucrose therefore for achievement of necessary level of sweet of products it is possible to use its smaller quantity and by that to reduce level of consumption of sugar that is very valuable during the development of diets of limited caloric content, napr, for having obesity (see) is acquired quicker, than. Excess of sugar strengthens formation of fat, and at the increased intake of sugar in an organism turning into fat of all feedstuffs — starch, fats of food, partially a squirrel amplifies. Thus, the amount of sugar to some extent can serve as the factor regulating a lipometabolism (see). The increased consumption of sugar leads to disturbance of exchange of cholesterol (see. Cholesteric exchange) and increase in its content in blood; besides, it promotes strengthening of putrefactive processes in intestines, negatively influencing qualitative structure of intestinal microflora therefore the meteorism develops (see). It is established that these shortcomings are shown to a lesser extent at consumption as sugar F.

There are data that F. plays a noticeable role in prevention and decrease in spread of caries of teeth (see).

Nek-ry researchers consider F. sugar, the most acceptable for food in modern living conditions, considering the accruing hypodynamia, nervous stresses, an endointoxication products of ichorization in intestines, the increasing number of corpulent people, etc. However it is necessary to remember that at long and uncontrolled use F. as foodstuff development of acidosis and other pathological phenomena is possible.

T. in view of its positive influence on fatty and cholesteric exchange and roles in prevention of caries of teeth it is even more often used instead of sucrose at production of confectionery and drinks, to-rye are especially recommended to children and people of advanced age. Use of glucosic and fructose syrup, or the corn sugar replacing usual sugar at production of ice cream, sweet curd cakes, confectionery, etc. is very perspective. Natural sources F. many berries and fruit are.

Bibliography: Gorodetsky V. K. and

Mikhaylov V. I. Definition of keto-sugars in biological liquids, in book: Sovr. methods in biochemistry, under the editorship of V. N. Orekhovich, page 120, M., 1977; To about - accurate N. K., etc. Chemistry of carbohydrates, page 16, etc., M., 1967; Petrov -

skiyk. Page and In and N x and N e V. D's N. Hygiene of food, page 70, M., 1982; With h e n M. and. Whistler R. L. Metabolism of D-fruc-tose, Advane. Carbohydr. Chem. Biochem., v. 34, p. 265, 1977, bibliogr.

V. K. Gorodetsky.

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